With the advent of 3e, D&D introduced the controversial concept of "wealth per level". This was the notion that a character of level X could expect to have Y gold pieces of accumulated treasure. This was immediately heaped with derision and scorn, not least because it was intimately tied to the notion that characters should be able to buy and sell magic items with relative ease.
However...
To a certain extend, some sort of wealth per level calculation is inevitable. After all, the game needs to provide some sort of guidance for DMs about how to construct encounters that will challenge the PCs without being hugely lethal. In order to have any chance to do this, the game needs to assume a baseline level of competence for the PCs.
Now, when establishing this baseline, the game can either assume that the PCs will have magic items or that they will not. (There is a third option, but I'll come back to that.) Now, if the game assumes that the PCs will not have magic items, this means that as soon as the PCs gain those items they are immediately more powerful than the baseline. And that being done, the balancing guidelines start to break down. Conversely, if the game assumes that they will have magic items, if the PCs do not then they are weaker than the baseline, and the same problem applies.
Since virtually all games grant magic items to the PCs at some point, it only makes sense that the game should assume that they do have items, and then it's just a question of how many - what "wealth per level" do they have?
(These calculations are actually even more important in a "bounded accuracy" system like 5e, where every +1 bonus to hit is a much bigger deal. It is with more than a little concern, therefore, that I greet the removal of any "wealth per level" guideline in that edition.)
Now, I did mention a "third option" above, and it is this: magic items become considered just another part of the character - Elric gains huge power from Stormbringer because that's where he's spent all his "build points", but if anyone else picks up the sword they don't get those powers. Which works... to a point.
However, I've been digging into the 3e wealth per level table quite a bit of late, and come to a couple of realisations:
- There's no actual formula behind the numbers in the table. That is, there is no way to take the character's level, perform a mathematical calculation, and end up with the correct WbL. Instead, it's inevitably a matter of looking up the table.
- That said, there is a method behind those numbers. The DMG also includes extensive tables for determining treasure for each Encounter Level, with a matching table giving the average result for each EL. The XP system is also set up so that a group that faces nothing but EQ-equal encounters will take 13 such encounters to reach the next level. Taking the average treasure for each encounter, multiplying it by 13, then dividing by the 4 PCs that the game assumes, we get a set of figures that is between 5% and 10% higher than the gains from the WbL table. And this is consistent across all levels. (The 5% offset is to account for the group using disposable items, items being damaged, and similar attrition.)
- What this means is that WbL is not actually a guideline for creating new PCs at levels higher than 1st. Instead, it is merely an expression of the likely amount of treasure that the party will have gathered in their travels. And that treasure will be in all possible forms - gold, equipment, magic items, gems, jewellery, artwork, etc etc...
- The corrolary to this is that a character who is created at higher than 1st level should, by rights, either be required to roll on the treasure tables 4 times for each level or should be assumed to have sold everything that was collected and therefore should start with significantly less than the WbL table actually indicates. If we assume a split of roughly 2/3rds 'valuables' to 1/3rd 'items', and that the items (only) get liquidated to half their 'book' value, that suggests a character of higher than 1st level should actually be equipped with approximately 80% of the gold that is indicated on the WbL table. The ability to build exactly the items gained grants an optimisation that is not possible to the PC who merely gathers items organically.
However, there is a further corrolary even to that, and it is that the designers of 3e missed a trick. See, the various numbers on the random treasure tables were, essentially, plucked out of the air. There's no particular rhyme or reason to them. And then the average results follow, and then the WbL table - and so there is no formula.
However, it's relatively easy (in theory, at least), to build things the other way around. Build a WbL formula, split that into 13 treasure packages, and then build the treasure tables to suit. And, indeed, there is a very obvious formula that really should be used in this regard - the expected WbL should be some multiplier of the XP gained by the character in the level. (In fact, in the early levels, WbL actually does this - for 4 levels it is consistently 90% of the XP total, before accelerating out of sight. But the best multiplier is actually quite simple: 1. Have WbL match the XP per level table, and you get a system that is much easier to remember and actually quite easy to design for.)
Of course, making that change would mean redoing the treasure tables, and would mean redoing most of the magic item costs. Which is an awful lot of work. But then, most of the item costs actually bear almost no resemblance to power level, not least because a character benefits a huge amount more from carrying lots of 'minor' items than he does from carrying one or two 'major' items - and that's an inevitable consequence of the way those prices are assigned.
(In fact, magic items are only balanced if they are found, and found mostly-randomly, and can neither be bought nor crafted. But that's another rant entirely, and one I'll go for on another day.)