There are some holes you should plug if they're not intended:
1. Epic Appraise
This ability effectively grants the character an improved, constant Detect Magic effect, because of the epic use of appraise:
The character can sense magical auras in objects.
Task: Detect magic
The character can sense if an item has a magical aura. He or she can then use Spellcraft to learn more about the item as if he or she had already cast detect magic on the item. This requires a full-round action.
So, by taking a single full round action, this character automatically gains the benefit of casting detect magic and concentrating for 3 rounds on an object.
This still doesn't brake the game (although the limited number of 0 level spells per day in 3.5 makes this advantage more tangible compared to PF for example). But you may wish to explicitly address this in the ability description (either allow or forbid it, as intended).
2. Unforeseen interaction with other exotic abilities
As Micha has demonstrated, there may be some unforeseen interactions with other exotic abilities, such as the Exemplar's Persuasive Performance.
The remedy (?)
It may be a good idea to phrase the ability so that it applies only for the two "standard" uses of the skill - appraising common items, and appraising rare/exotic items.
That should allow you to avoid all sorts of unexpected abuses.
Also, since this is a homebrew, the social contract can help you avoid bizarre, unexpected and unintended side-effects. This obviously depends on your group's way of handling house-rules, but unlike published rules, in this case you always have a clear idea of what are the RAI, and use that when your RAW yield funny results.
Other than that, you are probably fine
I doubt that the use of this ability as intended can have a major effect on the game. A level 14 wizard can easily have a +16 to +20 modifier in appraise(1), and much more if he uses magic / magic-items, while the DC usually won't be much more than 20 - 25. So auto-success isn't that far from the norm anyway,
Especially keeping in mind that:
- The only benefit of success is knowing how much an item costs.
- That still doesn't guarantee finding a potential seller (for items you wish to acquire).
- That still doesn't guarantee finding a buyer who'll pay that price (for items you wish to sell).
- Some people may be willing to pay much more than an item's actual worth ("that rusty old shield belonged to my great grandfather!").
- Some people may even object to the idea of certain items being bought or sold - valuable as they may be ("How did you get that angleskin armor anyway?!").
- Some circumstances may radically change an item's worth ("with all the rumors about vampire attacks, you'll pay dearly for garlic in this town...", also this).
So I wouldn't worry that much about it breaking the game.
(1) A 14th level wizard with +5 from Int, and 14 ranks in appraise (cross class skill for wizards) will have a +12 modifier.
Add to that a masterwork magnifying glass (+4), masterwork merchant's scale (another +4), or some other relevant masterwork tool (again +4), and you can easily reach +20 when at least two of these tools apply.