I know of no official source for this type of info. I was sort of hoping that the BoVD would have some but it doesn't. So, I came up with a basic framework that I use in my campaign. Like most things in my campaign, it is only as fleshed out as it needs to be in order to support the story so this system doesn't contain a lot of numbers. Feel free to use as much or as little as you like:
- If you are Evil, your soul is destined for Hell. Most likely you'll wind up as a Manes or Lemure but powerful folks who strike bargains with powerful Demons and Devils might secure a higher station for themselves, usually in exchange for some period of servitude.
- The various powerful lords of Hell have minions who gather these souls up and deliver them to the fortress of their lord. There, they are impounded and placed in large holding pens for later use. These pens of souls are the primary form of wealth in Hell. The Demon and Devil Lords issue currency against the value of these souls. I use only two denominations: Soul Cents (worth 1/100 of a soul) and Skulls (worth one soul).
- This money is paid as a bounty for the souls gathered up by the minions of the Lord in question. Usually a few Cents per soul are given as a reward for delivering the soul to the Lord's pens. These Lords also give payments for special services rendered to them by the Demons and Devils they employ. In this way, infernal creatures build up wealth.
- They spend this wealth in a variety of ways. The most common is payment for other infernal creatures they summon. You know how many of the Devils (for example) can summon X number of Lemure's Y% of the time or W number of Baatezu (usually similar to themselves) Z% of the time? I roll those in advance and determine how much "cash" the Devil has based on that. For Lemure's, each Lemure he can summon represents one full soul worth of money. He's making a "temporary withdrawal" on his account but any Lemure's destroyed in the ensuing battle are not deposited back in his account and are debited. As for the other Baatezu, they are summoned contingent upon them being bribed, either with cash or with promise of reciprocation in the future or some other favor. If the Demon or Devil in question fails the percentile roll, you can bet that he is cash poor or has a bad credit history.
- Another popular way to spend your cash if you're a Demon or Devil is to pay to have the local Lord make you more powerful. This could take many forms including purchasing magical items, advancing your Hit Dice or (the biggie) promoting you into a higher order Demon or Devil. In all cases, you must pay handsomely for these services and your account must be reconciled against any past withdrawals made by summoning Lemures or Manes.
- If all this sounds like a lot of paperwork, you're damn right it is. Fortunately, Hell is well staffed with accountants and lawyers.
- Because most of the Souls on which this economy is based tend to concentrate themselves in the pens of the Lords of Hell, and considering that there is a constant influx of these souls, these pens would rapidly become overcrowded if nothing were done with the souls. That's why most Demon and Devil Lords have strong Public Works projects going on most of the time. These souls are put to use building roads, bridges, weapons, walls, etc. Almost any structure in Hell is built by the Artificers who work for the Lords, hammering these souls into new forms and shapes. Lords of Hell take pride in making their domains impressive and awe inspiring. It attracts higher quality help plus these projects help keep the lesser Demons and Devils busy, giving them less time to plot revolt.
- One result of all of this is that infernal beings are always eager to get to the Prime Material Plane. Once there, they have the opportunity to corrupt individuals into promising their souls directly to the Demon or Devil in question, cutting out the middle men (the Lords) and maximizing profit. The best possible scenario for the infernal being in question is to get a powerful mortal to actually sacrifice souls to them on an ongoing basis. Too much of this however may raise the ire of the Lords of Hell who are being deprived of their cut. This frequently leads to open conflict but can sometimes be smoothed over by politically minded Devils (this happens less frequently with Demons). Fortunately, like accountants and lawyers, Hell does not lack for politicians.
Perhaps some of that might be of use to you.
