In developing Fractured Kingdoms one of the core concepts was keeping the rules as simple and streamlined as possible. In doing this I did away with a traditional currency system. Instead purchases are made through a roll versus the Purchase Value of an item.  This was done to keep purchasing gear in line with other system interactions and to allow for intangibles like finding a deal running short on cash and to a greater extent being able to use things like contacts and favors to increase the character's effective buying power.

However, in a recent play test the strongest criticism I received was not having a tangible dollar amount for how much money they could take from another player. The system as designed would offer the characters a temporary wealth rating to represent a one time windfall. However, the argument was made that this is too different from traditional role playing games and difficult to understand.

So I'm reaching out to the Force community for feedback and thoughts on these ideas.

I would guess that it depends on how much the economy matters in your games. For instance, White Wolf always used a stat called Resources that goes from 0 (broken) to 5 (filthy rich) and if it makes sense that you can buy the item at your wealth level, you do, at Storyteller discretion. no roll or bookkeeping involved.

A way to fix your rules might be that instead of giving a fixed amount of money to another player, you might give them a dice roll that is equal to or less than what you can roll yourself that the other player might "cash in" by using that roll instead of his own. You would also need a rule on how players can combine their wealth to buy bigger stuff and when do their wealth diminish.

Certified wrote:
However, the argument was made that this is too different from traditional role playing games and difficult to understand.

If players actually need solid numbers at some point, and having the narrator assign them arbitraily isn't enough, perhaps a table to convert the rolls to actual numbers would do the trick, if your dice mechanics can't solve the numbers issue by itself.

Donjon's Money and Goods comes to mind. There's a score for wealth and a score for provisions. When spending, you can add dice for wealth, but when succesful you lose the amount of dice you added. When you gain wealth, you roll to check whether the gain was significant enough to boost your wealth score.

I haven't had a chance to playtest this system yet, so I might be talking out of my ass, but:

In my homebrew, we have a dual resource system. First, you have your Resource score, which is exponential and represents sources of income and so on. If an item is a certain amount of steps beneath your Resource score, its monetary value is of no consequence to you. For a normal person, this could represent a meal for a day, while for Bill Gates it could be a sports car - and for a nation it could represent something really big; a batallion of soldiers or something. Purchasing these items puts no immediate drain on your cash flow, so it's not really interesting to keep track of. If an object is close to your Resource score, you roll to purchase it. The rationale behind this is that it's only interesting - from a gaming standpoint - to keep track of whether the PC manages to purchase items that are important (either to the character or to the story). If the character is filthy rich, a handgun isn't gonna set him back any noteworthy percentage of his assets. If a character who needs the handgun has some reason not to be able to purchase it (as in, he's not that well off), that's when money gets interesting.
You also have Treasure. Treasure is stuff which has a monetary value, but which generates none. While a farm or a spaceship or stocks in a company would be considered reasons to have a high Resource rating, a briefcase full of cash, or a bag of precious gems, would be considered an item with a fixed Treasure score. Treasures can be used as a one-time boost to a resource roll.
If you fail your roll to purchase an item, you can either sell off resources (and get a number of points of Treasure for each point of Resource), or opt not to buy the item.
In this system, you can represent tangible monetary assets as Treasure - and thus you could easily say to a player that they find a pouch with 10 gold pieces in it (let's say that 10 gold pieces equals 10 points of Treasure, for simplicity's sake), and have it mesh with the system.

The reason we chose to handle money in this way is... Well, beside the fact that keeping track of every penny is time-consuming and Not For Us, the game supports both political/social playstyles as well as post-apocalyptic dungeoneering. The system can both reflect people with steady streams of revenue, as well as characters who find a stash of valuables while searching a pre-apocalypse bomb shelter.