Kaiju had a two part series on money starting with the an abstract wealth system and moving to more detailed systems used elsewhere. This got me to thinking about wealth systems and what it means to the stories and tales that we tell - and how they are dependent on the mechanics.
In an abstract system, the importance of money is diminished in the game, in my experience. Rarely is the story about whether there'll be enough money to buy bullets, food, or keep the ship in the air, but instead generally about favors and obligations instead. Because generally there's a limit to the amount of things Wealth can do, for example having five dots in Resources means there's no where else for a character to go for money. It makes tales about hard scrabbling difficult, one because there's little granularity in the system, and second because you bump into a case of not really having a good reason to do a job for cash - "well a $500 bucks isn't going to actually boost my resources score, so why am I doing this again?"
In a dollars and cents system, the stories tend to be more about acquisition because there IS no finite limit to the amount of wealth you can have. You can always hit another dragon's lair for more treasure, or raid an arcology for another piece of hot tech for Mr. Johnson, or some other mad money making scheme with your free trader. But it involves a lot of book keeping, especially if you use multiple currency, and also inflation is a problem.
Coming up with a solution that works in all situations is a bit of a holy grail - as Marshall noted at Division Nihil, where he says
A wealth system should be able to handle several important story functions. The characters should be able to be stripped of their resources and forced to scrabble to survive. Common, everyday expenses should be able to be easily ignored. (These two goals are very difficult to reconcile.) The players should feel strongly rewarded when they either find a large treasure or get paid a large fee. A character should be able to be designated as "rich" mechanically, with significant bonuses as a result. The economy of the setting should either make sense within the rules, or be abstracted to the point that the characters have relatively little impact on the wider economy.
Diaspora, which is based on Fate, got around some of the problems of the granular system by introducing a "Wealth" stress track, basically large purchases caused damage to the track and and eventually caused the characters to suffer consequences, consequences which then made it subsequently easier to take a character out of a conflict. Yes, being behind on your bills could make it easier to knock you out of a fight. The joys of a narrative system.
As Kaiju noted - Conan d20 got around the inflation point by causing the heroes to spend 50% of their wealth in "high living" -- drinking, wenching, feasting, repair and equipping. Shadowrun did something similar with different standards of living.
I prefer the abstract wealth systems - mostly because it stops me from having to care about figuring out how to separate characters from their wealth. Without some sort of mechanic inherent in a granular system to remove wealth from the players just continues to grow until it reaches preposterous amounts (aka fundamentally the "wealth has ceased to be a motivating factor" issue within abstract systems).
But an abstract system does force the game to be about different things - as a rule hard scrabble existence will not be a driving motivation for the characters. Equipment, outside of special gear, will not be a driving force because the conversation goes along the lines of: "I want to buy this." "Are your resources high enough?" "Ayup." "Done."
So what can you do with abstract systems to make them motivate - there's making buying the next level cheaper. "So what do we get paid for this?" "Enough for me to give you a 1 xp discount on buying the next level of wealth." Yeah, it is a conceit to the system, but it works well enough for me.
There's going to be no holy grail - therefore, I look for the system that lets me tell the story I run - ones where wealth is merely a tool for clearing out common obstacles and let the rest of the problems be ones that money can't solve. Admittedly, this eliminates as a rule the idea that characters shall be "stripped of their resources and forced to scrabble to survive" but I'm okay with that, it isn't a story I want to tell, often, and when I do, I can arrange it so that benefit is unavailable when I do, rarely, run a plotline that calls for wealth to be unavailable.