On the gleemax forums I've extensively discussed the
Negative Difference Engine and its attendant problems. I've also discussed some algorithms for wealth optimization, but those algorithms do not necessarily translate well into practice (they're ultimately looking at average expectation, something no given character will ever see).
Which leads us to the very practical concern of optimizing wealth acquisition for a given party. I say party because a party is the unit which acquires wealth, and has to divide that wealth amongst its members. So you can't just optimize one character, you have to optimize your entire party simultaneously. I'm going to assume default party sizes (ie, 5 characters).
General Principles(1) Casting rituals is bad for your wealth. Don't do it.
(2) Minimizing potion use is good for your wealth. This implies that certain party compositions are probably better than others (eg, 2 leader parties), and thus even party composition is an arena within which party wealth can be optimized.
(3) You should aim to only replace items that are significantly below your current level.
(4) Items you will never replace are preferable to items you will. Ie, my Brace of Wands post provides a mechanism by which a wizard can temporarily upgrade his implement for high paragon levels, and keep that implement till the end of epic, thus never selling said item. (Note that even orb and staff wizards can use this, because nothing about orb or staff mastery requires you to actually cast spells through an orb or staff).
(5) An item you would never use is a 100% loss. (You should recycle items which will never get used).
(6) A character must be viable at every level.
The effects of 1+2 dominate at low levels, and become less and less significant at higher levels (although excessive potion use or repeated high-level ritual use even in epic will certainly be noticeable). The effects of 3+4 will dominate high levels, because wealth lost to replacing items will become more and more significant.
Benefits of Wealth OptimizingIf the idea that wealth = power because you can turn wealth into magic items isn't a sufficient justification, consider that every extra item you acquire will either (a) have a useful property or (b) have a daily power. Properties have no limit on their use aside from your having a limited number of item slots in which to put them. Daily item powers are limited to 1/tier +1/milestone, which means at epic 5-6 daily item power uses/day should be common.
Items which have properties will be unlikely to be swapped frequently. But one might imagine a character having a different item set for adventuring than for social interactions (ie, a town set and a dungeon set). Certainly, having excess wealth would aid in acquiring the appropriate items to do so.
Item daily powers in excess of the number you can use per day obviously aren't being used. But which ones are being used will vary from day to day. Thus, more daily item powers, more options. And many items *only* have a daily power use - such an item can be swapped out between encounters when it has been used, allowing a different item to take its place. Alternately, weapons or implements with daily powers may have specific uses that having a swap is a viable strategy - most notable with wands for which two useable powers gain +4 to hit against single targets, and thus can be viable after the enhancement bonus of the item itself is considered subpar. Wands can also have utility powers, with the obvious advantages gained by having them. Some other implements have secondary powers which don't require the implement in question to have been used to channel a power in order to activate them - these obviously don't care what the item bonus is. Making a case for any weapons is harder, but I won't rule it out.
Obviously, characters who need multiple types of items from the weapon or implement category are going to be at a disadvantage relative to other characters, and therefore care about wealth optimization solely to try and play the same game as their buddies. This is especially egregious because the big 3 (weapon or implement, armor, neck item) are going to be your major cost in terms of losing wealth to item recycling - making that the big 4 is a large hit.
Problems with Wealth OptimizationIts no exaggeration to say that this is a *hard* problem. (NP hard to be exact). Mathematically its a packing problem. If that wasn't enough, there are other difficulties:
(1) It is build dependent. Different builds will want or desire different items, which will have different levels, and thus pack differently into the parcels received. Some classes or builds are more or less capable of taking advantage of various general principles, meaning there's no well defined maximal optimization.
(2) It requires negotiating with 4 other players about the distribution of 30 levels worth of items. Either everyone is on board with optimizing this or there will be annoyed buddies or hurt feelings.
(3) Optimal solutions may not involve equal wealth per player (in fact, they likely won't).
(4) Desirable items aren't distributed uniformly across level. There will be level N items for some N which you may have a hard time packing items into. Other levels will be overloaded, and you'll need to find compromise items. Ie, its not only a packing problem, its a packing problem with highly non-uniform pieces, and they vary in unpredictable ways. (More supplements with items will help alleviate this, because it will tend to create desirable items at all levels).
(5) Obviously, some players may be more or less willing to compromise, and this leads to a complex haggling minigame within which various game theory models of behaviour, trust, reputation, etc..., likely apply. This is *complicated*, and at best at the cutting edge of research in game theoretic topics.
Doesn't the DM Control Treasure?Ok, first of all, the best way to know what items will be of interest to your players is to, well, *ask* them. The DMG then goes on to say you should do exactly that. The thing about wishlists is you can game them, by limiting the amount of information you give your DM. Lets say you're level 13, and the players have optimized their treasure progression, and you're supposed to get an Iron Ring of Dwarf Lords in the next level. If you only tell your DM "I'd really like an Iron Ring of Dwarf Lords" he can (1) give you what you want, (2) give you something else that you're likely to not want at all, and thus defeat the intent of the treasure system. Ie, the information you communicate to your DM colors what he gives you.
Rather than making individual wishlists, the party may well provide a group wishlist. (And it can be perfectly reasonable that the party wizard is interested in the tank receiving certain items if the tank is keeping them alive!)
Finally, if there exist available item substitutions, you can provide a list of all the possible items (with or without explicit or clauses). There are going to be obvious substitutions based on item levels. A party will ultimately receive 4 level 15 items, and it really doesn't matter (from an overall optimization standpoint) which order they receive them in, so that level 13 character may make his wishlist to include any items the group has decided he should get of levels 14, 15, 16, or 17. This provides the DM with a diverse wishlist which also adheres perfectly to the party plan.
Another type of substitution if there are two items that fulfill the same function that are equally viable, such as two different +4 wands that a wizard is interested in. Saying "I'd be interested in this one or that one" as part of his wishlist is quite reasonable. More complicated substitutions can also be imagined. Lets say Character A would be happy with item a1 (of level x) or item a2 (of level x+1), and Character B would be happy with item b1 (of level x) or item b2 (of level x+1). They could agree to list both "a1 or a2" on A's list, and "b1 or b2" on B's list. This gives the DM some real choice (as opposed to illusion of choice) while letting the party optimize its wealth. And I can construct more complicated substitution schemes, but I think the point is made.
Ie, even if you assume the party doesn't have complete control, they still have some control, and can thus still optimize. There are even entire areas of applied mathematics interested in similar problems. Basically, party treasure received is some function f(x,y) determined by f(x) and f(y), where f(x) would be party input and f(y) would be a random factor (relative to the players). The degree to which the DM doesn't follow f(x) (ie, the less weight f(x) receives relative to f(y)), the less benefit can be obtained by optimizing wealth. The quoted DMG text is effectively saying "f(x) should receive a strong weighting". It won't necessarily be 1, but it should be a significant determiner of what the party receives.
Conclusions4E created the possibility of gaming the wealth acquisition system. This leads to a rather complicated wealth optimization minigame. Its also unlikely to be an enjoyable minigame for most people. However, it can be done, and the possibility of doing so may well color use and enjoyment of the game as a whole, even if done on a micro level (ie, projecting over the next few levels).