"You told me to go back to the beginning. So I have."
For PCs, I suggest following the Epic Level Handbook (EL) (July 2002) on Monsters as Epic Characters that, in part, says
[T]he effective character level ([hereafter] ECL) of any creature more powerful than the standard races in the Player's Handbook is equal to the creature's Hit Dice [hereafter HD] and class levels (if any) plus its level adjustment [hereafter LA]. This replaces the rule in the Monster Manual  that states that a creature’s "monster level" is equal to its Hit Dice.
Regardless of its ECL, a monster with class levels uses the base attack bonus and base save bonus progressions of its class (rather than the progression shown on Table 1–1 [that's on page 6 of the EL]) until it has 20 character levels. Beginning with its 21st character level, it uses the progressions shown on Table 1–1.
In any other place in this book [i.e. the EL] where "character level" is indicated, you can use [ECL] instead. For example, a creature with [LA] +5 who is also a 13th-level fighter/3rd-level blackguard is ECL 21 and eligible to select an epic feat provided he meets the prerequisites. (25)
If you change the heading to Monsters as Epic Player-characters and Cohorts, these rules are fine and playable. Here's how they shake out for the question's characters:
The natural werebrown bear human paladin 7. The creature possesses 7 class levels and gained 7 HD from those class levels. The creature has 6 animal HD as a werebrown bear. The creature has LA +3 as a natural lycanthrope. The creature's ECL 16.
The creature advances normally for 4 more class levels until it's ECL 20 with 11 class levels. When it advances another class level after that, the creature becomes epic, its 12 class levels making it ECL 21.
The locathah cleric 3/wizard 3/mystic theurge 7. The creature possesses 13 class levels and gained HD 13 from those class levels. The creature has 2 humanoid HD from being a locathah. The creature is unfairly burdened by a wholly unreasonable LA +1 as a freakin' locathah. The creature's ECL 16.
The creature advances normally for 4 more class levels until it's ECL 20 with 17 class levels. When it advances another class level after that, the creature becomes epic, its 18 class levels making it ECL 21.
All creatures accrue full benefits from class levels until they possess 20 class levels. Starting with their 21st class level, creatures receive the reduced benefits from class levels as per the EL's Table 1–1. HD that are from sources other than class levels always yield their normal benefits.1
If you, dear reader, don't care how I reached this conclusion, and you don't care about NPCs with LA (and their wealth!), then you really don't need to read any more of this answer. If you're the DM, though, remember this answer when you're stuck for how much gear that magmin Rog19 should have—that's addressed below.
As always, LA's the problem (especially with NPCs—but it doesn't have to be)
LA impacts only a handful of game elements. It affects how much XP a creature needs to advance a level. It affects when the creature becomes epic (therefore when it can take epic feats). And it affects the creature's gear. DMs usually don't worry about the XP for NPCs, but DMs tend to worry about NPCs' epic feats and gear. However, while the game predicates several rules on ECL, the game doesn't provide LA for all its creatures, and many unavailable-as-PCs creatures should have significant LA by the game's own evaluative methods (as Savage Species (Feb. 2003) describes) if the DM is expected to check an NPC's ECL. It's as if the game forgets that not every creature has LA. For instance, Monsters as Epic Characters, in part, says
The epic rules in this section also work for monsters with character levels [n.b. not just PCs with character levels but also monsters with character levels], using the creature’s effective character level [i.e. class level + HD from other sources +its LA]… instead of just its class levels. (Dungeon Master's Guide (June 2003) 209)
Further, Monsters and Class Levels, in part, says
If you choose to equip a monster with gear, use its ECL as its character level for purposes of determining how much equipment it can purchase. Generally, only monsters with an Advancement entry of "By character class" receive NPC gear; other creatures adding character levels should be treated as monsters of the appropriate CR and assigned treasure, not equipment. (Monster Manual (July 2003) 291)2
To make matters worse, the Dragon #310 (Aug. 2003) Wizards Workshop column "Sage Advice: The Sage Goes 3.5: Official Answers" includes this exchange:
When is a monster character considered epic level? Do you "go epic" when your total class levels equal 20 or when your total Hit Dice equal 20? Is a monster character eligible for epic-level feats… when its character level is 21+ or when it's ECL is 21+?
A monster becomes an epic-level character when its character level hits 21, just like any other character. A monster's character level equals its racial Hit Dice + class levels. (See the second sidebar on page 25 of the Epic Level Handbook [that's quoted above—except that in context when the EL says character level it means only class levels, not class levels plus HD from other sources].) A creature's ECL has no effect on when it becomes an epic character, although once it becomes an epic character, its ECL continues to affect how much experience it earns and when it can add a new level. (99, emphasis mine, and repeated on Main FAQ 5)3
Finally, worst of all, as part of an exchange that seems exclusive to the Main FAQ, there's this:
Use the character's ECL to determine starting equipment and how the character earns and benefits from experience (including when he gains an epic attack and save bonus; DMG 209 [actually 206]),4 as noted on page 5 of SS. Use the actual character level for everything else. (2 and footnote mine)
The DM must determine what to do about this big, angry pile of rules with regard to NPCs. Compare the creatures below.5
- The CR 17 aboleth mage (Monster Manual 8–9). The creature possesses 10 class levels. The creature has 8 aberration HD as an aboleth. The creature's LA —. Either it's ECL 18 or its ECL is unknowable, in both cases because of that LA —. It has double standard treasure (an essential entry that's absent from late-game stat blocks) but no gear; an ECL 18 NPC normally has 130,000 gp in gear.
- The CR 16 hound archon hero (17–18). The creature possesses 11 class levels. The creature has 6 outsider HD as a hound archon. The creature's LA +5. The creature's ECL 22. It became epic last level and was eligible for an epic feat. (It didn't take one.) Its gear is valued at about 21,000 gp, or close enough for a level 11 NPC but a significant distance from the 265,000 gp the NPC hero should have for its ECL.
- The CR 17 frost giant jarl (122, 123). The creature possesses 8 class levels. The creature has 14 giant HD as frost giant. Although the frost giant has LA +4, the jarl has no listed LA. Either it's ECL 26 because it inherits the frost giant's LA +4 therefore the jarl became epic upon advancing to blackguard 3 or it's ECL 22 because it has no LA therefore it became epic upon advancing to blackguard 7 or its ECL is unknowable because it has no LA. Its gear is valued at about 40,000 gp, a little short of the gear for a level 14 NPC and a far cry from the recommended 265,000 gp (if ECL 22) or 390,000 gp (if ECL 26) in gear that the NPC jarl should have for its ECL.
- The CR 13 celestial charger (249). The creature possesses 7 class levels. The creature has 8 magical beast HD as a unicorn. The creature's LA +8 if it's a cohort. Either it's ECL 23 because it inherits cohort LA as a normal NPC therefore it became epic when it advanced to cleric 6 or its ECL is unknowable because cohort LA is different from normal LA. ECL 23 means 290,000 gp in gear.6 It has none.
Obviously, there're substantial differences here. For consistency and verisimilitude, the DM must make a decision. I can imagine three options; readers may have more.
The DM rules that every creature has LA and assigns LA — creatures LA +0 or higher. The DM can use the methodology from Savage Species, harken back to the never-updated-for-the-3.5-revision Dragon #293 article "Monsters with Class" (52–5), or just make up a number, but every creature that's LA — is at least LA +0 instead. PCs and NPCs now have parity, but the DM must rewrite a significant number of monsters because they're woefully underequipped.
The DM rules that some NPC creatures have LA and some NPC creatures do not. The DM rules that an NPC that has LA — is effectively LA +0 and also rules that an NPC with at least LA +1 factor its LA into its ECL. PCs and NPCs that are playable as PCs (i.e. creatures that have LA +0 or more) now have parity, but the DM must still gear up a few underequipped monsters.7
The DM rules that only an NPC's class levels plus the NPCs HD from other sources count for toward its ECL, ignoring LA for NPCs. The big picture is that PCs that possess LA, uniquely for their kind, get access to epic feats earlier than comparable NPCs.8 There's no parity between PCs and NPCs, but the DM only has to rewrite a few monsters.
I've experimented with all of these, and I always end up at #3. LA is primarily for players and their cohorts, so the DM gets to ignore it, and I'm done.9 Using #3 means the aboleth mage, hound archon hero, and celestial charger aren't eligible for epic feats, but the frost giant jarl is. That sounds good to me.
Now let's talk about gp. Because #3 ignores LA, the value of NPCs' gear—for the most part—drops precipitously, but ECL remains a factor for NPC wealth according to the Monster Manual. The NPC aboleth mage's defeat still yields 130,000 gp in gear, but the NPC hound archon hero's down to 100,000 gp in gear, the NPC frost giant jarl's down to 265,000 gp, and the NPC celestial charger's down to 59,000 gp. But while this is less gear, it's still too far much. For instance, an encounter level 17 encounter like with a lone CR 17 NPC aboleth mage or NPC frost giant jarl should only yield an average of 36,000 gp (DMG 51).
So I suggest just ignoring the above from DMG, the MM, and the FAQ with regard to NPC gear and using instead Monsters with Classes that, in part, says
To determine treasure for monsters with class levels, first give them equipment. Use Table 4–23: NPC Gear Value… and use just their class levels to determine the value of their equipment. Then generate their treasure according to their monster entry and the rules under Building a Treasure…. This may generate more items that the monster can use, and that's fine…. (DMG 51)
And I suggest using NPCs with Treasure that, in part, says
The gear that NPCs carry serves as the bulk of their treasure.… NPCs may have treasure in addition to their gear, at your discretion, but an NPC's gear is already worth about three times the average value of a treasure of his or her level. Defeating NPC foes brings about great reward for treasure-seekers, but since the gear is mostly magic that the NPC can use against the characters (some of which is one-use), it all evens out. (55 and emphasis mine)
Using these rules in combination means that the NPC aboleth mage may have double standard treasure for its CR 17 plus its 16,000 gp in gear for its 10 class levels, the NPC hound archon hero may have standard treasure for its CR 16 plus its 21,000 gp in gear for its 11 class levels, the NPC frost giant jarl may have standard treasure for its CR 17 plus its 9,400 gp in gear for its 8 class levels, and the NPC celestial charger has no treasure for its CR 13 plus its 7,200 gp for its 7 class levels. This is more treasure than the creature's typical treasure—obviously, and especially if you're hunting unicorns—, so the DM still must be careful, but it's not the incredible lootslosion that defeating NPCs yields with the alternatives.
1 Epic creatures with class levels that also possess HD from other sources may have base attack bonuses and saving throw bonuses that are impossible for epic creatures that possess only class levels to achieve. First, that's exactly what the MM actually does, and, second, PCs that have HD from sources other than their class so rarely benefit from them that I'm okay with that.
2 Although the MM implies otherwise, it's only a choice to equip with gear a monster that has class levels insofar as obeying any rule is a choice. That is, monsters that have class levels always have NPC gear.
3 The Sage here is Skip Williams, the primary author of the Monster Manual for Third Edition. About a year later, with Dragon #223, 3.5 revision architect Andy Collins starts providing Sage Advice.
4 Reading that parenthetical cost you 2d6 SAN. Go ahead. Read it again. That parenthetical means rewriting every HD 21+ monster. Seriously, no printed creature follows that.
5 There're more creatures to dissect. If you're soldiering on alone, don't rend your garments: The premium Monster Manual (2012) changes the sample elite vampire's LA +8 to LA +5.
6 "What could a unicorn possibly do with all that gp?" you ask. The celestial charger has Int 13 and Wis 27, so I think the answer is, "Spend it well and wisely."
7 This idea has merit, but it makes some NPCs eligible for epic before other comparable NPCs solely because the former's LA +1 or more and the latter's LA —. For example, a CR 15 troll Rgr10 (monstrous humanoid HD 6, class level 10, and LA +5) can have an epic feat, but a CR 20 wraith Wiz15 (undead HD 5, class level 15, and LA —) can't. The DM should make this clear before the campaign begins as it directly impacts how players judge NPCs.
8 Not incidentally, PCs will also have significantly more gp than comparable NPCs. They'd have more anyway because they're PCs, but still.
9 A creature with LA +1 or higher that becomes a PC's cohort may find itself eligible for epic feats. It also may lose that eligibility if its association with the PC ends. I suggest the DM doesn't have a cohort take an epic feat until the cohort would be eligible to take an epic feat as a normal NPC (rather than as a cohort), but I suspect the entire issue is unlikely to arise.