Shadow of the Demon Lord has a nice, simple Standard of Living thing it does, but it can still result in bean counting. I would also check various incarnations of Fate for a “Resource” stress track (e.g. Bulldogs), Barbarians of Lemuria for a cool system that sees the PCs forced to blow all their treasure before they are allowed to earn XP, and King of Dungeons for a take on treasure that has the PCs track resources in three areas: Kit, Coin, and Lifestyle. Pretty cool.
My favorite approach, and one of the simplest, is to abstract it away with a Black Hack style Usage Die – as seen in Sharp Swords & Sinister Spells. So rate your Wealth with a die value, say a d6. When you want to use it to buy something significant, roll it; on a 1-2, it shrinks to a d4. If you test that d4, rolling a 1-2 means you’re broke and can’t afford anything that costs serious coin. You could use advantage and disadvantage to model items that are particularly cheap, or expensive, without having to put price tags on everything. I also like the idea that a nice haul might mean you go ‘up’ a couple of dice bands, say taking your d6 Wealth Die to a d10. Carrion Lands also takes this approach, and uses a similar resource / usage die for food, water, blood… and even doom.
Agree it would be a fun topic to hear the guys muse about.