Yes, Last Breath in a magic trap removes the XP and amortizes the money requirements at the cost of a planned suicide and a very expensive magic item. The rest of this answer will explore if a village of 57 commoners can achieve this magic trap in one lifetime.
... some math later...
They can achieve practical immortality in about 5-10 years of sitting around blissed off their gourds and writing poetry.
Many of the mechanics of last breath and why empires like this form the campaign settings of the future have been detailed in my answer here.
In this question, however, we are begging the question of "can this be done by a level 1 commoner?"
First, don't underestimate a community of optimised commoners (where this sort of cheese is likely to take place.) They can do some quite remarkable things by working together over periods of time.
We'll ignore the Henry Ford of commoners, however, and assume that they haven't mastered the modern assembly line. We'll also assume that this project is generational (for given values of generational) and that there's a friendly order of archivists around who would be very curious to see how this sort of thing turned out.
We have a number of hurdles for our community:
- Getting enough food to live on
- Making a surplus of money
- Defending against nominal threats
- Buying a iron maiden of eternal life (64000 gp, kills someone entering it and casts last breath on their corpse).
- Fighting off the maruts that decide to be annoyed at the community.
Crafting food to live on shouldn't be a matter of survival checks, as they presume a hunter-gatherer lifestyle. We will presume that we're a trading village, as I don't feel like exploring the "economics" of farming. Therefore we will presume that we sell our goods to their lord, representing a very generous tax rate of 50%. (For the times, this is generous, but whatever.) For sake of argument and to simplify logistics, we will presume that this village is owned by a monastic order of archivists who can defend them from most normal threats in exchange for the taxes.
How many people does it take to feed this community?
Now, clearly, magical items are the way to go here (eventually). A commoner can expect to live at least 50 years. (Which is long for a fantasy time, but whatever.) Over that time, she will expect to spend 1 silver per day on "food" for the totality of her life. Now, we will presume a community with dedicated cooks, such that they can make craft checks for this purpose. We will say that a poor meal is easy, with a DC of 10. The chef (having a positive intelligence), will have a check of 10 (taking 10)+1 (int bonus, being conservative)+2 (masterwork tools, since 50gp pots are a great hand-me-down)+4 (skill ranks)+2 (feat:apprentice (craftsman)) = 19. Apprentice(craftsman) further reduces the goods cost by 10%. She'll need one assistant (the apprentice-apprentice cook).
Therefore, assuming that we can batch up days of food into some unit that the math likes (approximating the daily grind of making bread and porridge), our chef will voluntarily add +10 to the DC of the item, making 400 sp per week worth of meals, or approximately can feed 57 total people for the cost of 120 sp.
We will therefore set our village size at 57 (or some multiple thereof)
The cost of feeding a village of 57 people for 50 years is therefore, 31200 gp, give or take feats. Having 6 assistants helping doesn't actually provide for higher productivity per person, so our chef won't use more assistants than necessary. With a trait, she doesn't need the assistant, but I'm hesitant to bring in UA stuff if I don't need to.
Since there are no rules for logistics chains, we don't gain anything from having a stack of value added "farmers to millers to chefs". Therefore, we're looking for the best skill RoI to feed the community.
To see if we can get to functional immortality, we'll have a budget of 2850 peasant years.
Making money by writing words
The best skill to earn money with is Craft(Wordsmithing) (Races of Stone), which for a fixed 2GP per week, can generate reference books (dc 18, 100gp), epics(d20, 500gp), and symphonies(dc 20, 100gp). We'll assume that the archivist monastery that this village belongs to will happily purchase this output because they've figured out how to be a publishing house (and make oodles of money.)
Our author must be human (for the extra feat), and will take Hidden Talent (Minor Creation) and Psicrystal Affinity(Aritsan). while apprentice(crafter) and mark of making are also recommended by the handbook, I can't bring myself to accept flaws here.
Therefore, our middle aged artisan will have 10 (take 10)+4 (ranks) +1 (int, middle aged)+3 (psicrystal) +2 (masterwork tools), or a neat check result of 20.
Presuming that there's an infinite market for symphonies (And not touching the DMG2 business rules because no.), our artisan can gain 40 gp towards the symphony or epic per week. We will set the cost of the work at multiples of 40gp, depending on "market conditions." (We will presume a steady stream of commissions come from the monastery on the hill from their contacts. Dealing with infinite planes is very odd when thinking about economic situations. We'll assume there's a market and move on.) Unfortunately, this crafted object can only be sold for 50%. So we'll abstract this process to assert a commune of creative types making (20-2)gp per week, legally.
Therefore, we have 1 chef and her assistant, producing 400 meal-days per week for 12 gold. feeding 57 people on poor (but well made) rations. We'll assume 1 author (doesn't have to be the same person) producing 18 gp per week writing.
Given how much effort it takes to feed a community, we'll up the meal quality to common and triple the price (36 gold) and require two authors a week to produce works to feed the community. We've spent 4 people so far.
It's going to be very very important to avoid building up liquid wealth beyond the village's capabilities of defending it. It's also important for the village to build up sufficient wealth to buy an Iron Maiden of Eternal Youth.
In the Magic Item Compendium, a field provisions box is 2000 gp, and feeds 15 people per day. Since there's already an item that does this, we won't work through the costing of a magic trap of cafeteria steam trays. It costs a little over two years of profits of our typical wordsmith to buy one of these. The village will need 4 of them total, but assuming we have a writing community of 8 more people (bringing us to 10 creatives, 2 cooks), We can have the village self-sufficient for food in a year.
Food self-sufficiency costs the village 36 peasant years, bringing our budget to 2814.
Liquid Joy, the main product of the village
The next bit is rather sketchy, as it uses spells from book of exalted deeds. Specifically, we'll need to invest two spells into magic traps: Elation and Distilled Joy.
The most profitable use of sentients is in the production of XP for magic item creation (assuming that we're trying to generate wealth instead of just reallocating it in the usual murderhobo fashion.) Conservatively, 1xp in magic item creation is worth 5gp. Distilled Joy takes a day to produce, and provides a vial which good spellcasters can use as the equivalent of 2xp.
Spending a day in the hall produces a vial of ambrosia worth 2 xp or, by definition, 10 gold. Therefore a villager can produce a profit of 5 gold a day by listening to nice music in the hall and experiencing joy. Technically, ambrosia is worth 200 gp on the open market according to the book of exalted deeds, but we'll ignore that because that makes the village too rich too fast.
The basic process will be a magic trap of elation inducing elation inside its radius. This trap will cost 6000 gp (CL 3 * spell level 2 * 500) *2 (to represent an NPC crafting cost, just like normal "magical items") Also included in this room-wide "magic trap" will be the distilled joy spell, for an extra 15000 gp for a nice total of 21000 gp to make an auditorium, 80' in radius, where audiences can enjoy novel symphonies and other artistic works (since we have the creatives on staff, we might as well use them.) After our 10 creatives buy four field provisions boxes, they'll produce works for 2.3 years to pay for the creation of this auditorium. Every 18 seconds, another wave of elation will fill the auditorium, and another person (in rotation) will have distilled joy cast on them.
We'll assume that this auditorium has 20000 square feet of "enchanted" space, and, since we're designing the space for maximum comfort, we'll allocate 300 square feet per person, easily allowing the entire village to fit beds, tables, and chairs in. Given the casting time of 1 day for distilled joy, we'll require that a villager spend a day in the hall to generate the ambrosia. We'll ignore the various ways of getting a spell cast more quickly.
Creating this infrastructure will cost the village another 30 peasant years. (I'm rounding up to account for natural friction.) Leaving us 2784.
Defending Against Nominal Threats
We'll assume that we ask for half of the village to be in the happy-house every day (or 28 people). And that these people are not otherwise productive. (They'll be supplied any book they want to read or art supplies or conversational spaces or performances, but we won't price their output.)
Every day, this produces 28 doses of ambrosia, worth 280 gp (or 140 gp to the villagers). Given that the costing makes it equivalent to a healing potion (on the averages), 5.6 bottles will be walked up to the monastery to be sold on account to the gods, good spellcasters, or used by the monastery. This leaves the guarding of liquid assets to the monastery. Two major defensive requirements emerge: defending the fixed investments of the village and defending the shipments. Because the ambrosia is restricted to good spellcasters, only evil spellcasters with use magic device, or chaotic evil "wreck everything" nutjobs will be interested in taking over the village.
These 28 doses per day cost the village 1400 peasant years. (Midway through, there's likely a rotating cadre of peasants, as the "be happy for a decade, and then get your youth back, free" deal is... not a bad deal. Still, that's outside the scope of the problem. This reduces our available budget to 1384 years. On the other hand, 28 doses per day generates 140 gp for the village every day. This means that in 450 days of joint work, the villagers could pay for their iron maiden of eternal youth.
Honestly, at this point, affording good ground and anti-air defenses is well within the village's capability before the iron maiden is ever used, And they've spent, at most, 5 years with most of their population available for defending the village. With the resources they can muster, especially selling soul-food to the good gods, it's very hard to see how they couldn't afford items of "Marut-b-gone" or just have a quiet conversation with one of the gods who likes their product along the lines of "hey, can you have a chat with those guys, they're threatening your food supply? Oh, by the way, would you like your next joy to be flavoured with a specially commissioned symphony or perhaps some delightful poetry?"
The main problem stems from the source of wealth: The Joyful Mind(Kringelbach and Berridge 2012) where direct stimulation of the pleasure centre decoupled from productive activity caused rats to push the pleasure button without ever actually gaining sustenance, leading to addictive and self-destructive patterns that use our own reward training mechanisms to defeat ourselves. See also: Omelas, Lotus Eaters.
So long as the joy was carefully rationed, with copious contributions of Remove Addiction and other necessary healing spells, this should work marvellously, leading to explosive population growth and the founding of an ancient empire that modern heroes can discover the wondrous artefacts of. And then they find the great hall... and everything starts over again.