Of course it's possible. But in a game you don't want to create the most detailed real world simulator but an abstraction of the real world that feels real enou

Of course it's possible. But in a game you don't want to create the most detailed real world simulator but an abstraction of the real world that feels real enough while at the same time is a lot easier to implement than the real thing. In MMO economies that usually means you have magic money creation boxes (mostly killing monsters or mining resources for unlimited sources) and money destruction boxes (e.g. repairing your items or paying tax/rent for different things). If you have more creation than destruction you have inflation, which is fine to a limited extend.