The first thing I think of when I think of dwarves is the treasure hoard under the Misty Mountain (yes, LOTR). Mountains and mountains of gold, gems, and treasures. What does one trade for, when one produces everything one needs? The answer is wealth. Treasure. My artisans work to produce masterworks, which in turn are traded to caravans.
Unfortunately, there comes a point where the caravans simply don't have anything I want. Massive amounts of wealth remain trapped in masterworks and artifacts that are simply worth more than anything I want from the caravan, and remain unsold, left in stockpiles to gather dust.
To be clear, I'm not talking about a full economy. Not right away, anyways. Nothing says I have to pay my dwarves with the money I'm making from their work. At the moment all this is, is a means of trading with caravans for dwarfbucks rather than just bartering.
Being able to accumulate raw dwarfbucks in dedicated treasure vaults... that screams dwarf to me. Having a monarch that demands more wealth, ditto. Having dragons come to claim my hoard, oh baby.
But there's a lot of future potential for economy: Your hoard of dwarfbucks, stored in your treasure vault, can be used as monetary backing for your coins.
When you mint coins of various types, they become worth portions of your dwarfbucks. If you've minted say, 100 copper coins, then each of those 100 coins is worth 1/100th of your total treasure vault. If you mint 100 additional silver coins, worth 5 copper coins (and having equal portions, your copper become worth 1/600th of your dwarfbucks, silver become 5/600th or 1/120th of your dwarfbucks). Add 100 gold coins, worth 15 copper ea, your copper coins become worth 1/2100th, your silver become worth 1/420th, and your gold are worth 1/140th. So on and so forth.
You don't trade your coins to caravans though as they simply won't trust you to redeem said coins for the intended amount of dwarfbucks, the same as I wouldn't be willing to trade dollars for some hyperinflated currency in the real world.
You trade raw dwarfbucks. Dwarfbucks effectively become what we use gold for in the real world. Coins become tender to be conceptually redeemable for dwarfbucks.
At that point, once you've got a functional currency system, turning dwarf pay back on is just one little step.