Rust monsters are iconic. Nightwalkers less so. But they can both destroy PCs' expensive magic items, placing the party far behind the wealth-by-level (WBL) curve. I might expect that, to compensate, they have increased treasure values (losing multiple 100k gp magic weapons to a nightwalker would require the game to absolutely shower the players with wealth to "make up for"), but this is not the case. Naturally, frontline fighters with lots of metal equipment are most susceptible.
Lots of undead are the opposite. They can give negative levels without affecting PCs' equipment, effectively putting them ahead of the WBL curve. Against intelligent undead, spellcasters with poor Fortitude saves will likely suffer the most negative levels throughout a campaign.
As far as I've read, the DMG doesn't say anything about "catching up" players who spend/lose a lot of money (but not levels), nor the opposite situation. It mentions that an otherwise-weak encounter could be an appropriate challenge if players don't have their equipment, but everything seems to assume that treasure rewards are tied to challenge level, so this doesn't seem like it would "correct" the wealth curve.
Do any of the books have any more to say on how (or even if) PCs should fall back in line with their expected WBL? Or on how to deal with PCs that are consistently not in line with it?