Does anybody else get unreasonably annoyed at the vast majority of rpg games that are feudal societys on a surface level but are actually capitalist societys under a thin vineer. I was trying to play pillars of eternity but became incredibly annoyed at the frist quest of the game revolving around a mill which is in a lord's domain but is privately owned and operated and which the townsfolk sell their grain to in exchange for currency (to later buy back with the same currency). I had to put the game down right there.
I think a lot of the time it's an outgrowth from developers feeling the need to have a commonly circulated currency. Although the answer in my opinion isn't to faithfully recreate feudalism but to create a unique social formation for the conditions of the world, I've always loved the eberron campaign setting for that reason.
My favorite "currency" is the bullets in Metro, since being able to shoot your money is an interesting piece of worldbuilding and an interesting gameplay choice.
Metro's bullet currency was such a great idea. It hammers in to your head that the technological mastery of the past is gone and it's never coming back. All you have to show for the past is shiny brass cartridges that might save your life, either because they can kill a Nazi before he can kill you, or because you can trade them for food and shelter. It's as far from a fiat currency as you can get. Every military grade bullet is rare and precious entirely because of it's utility, and the state of the world is such that no one would think of hording ammunition that could go to the rangers that defend the station from mutants and Nazis.