I'd just let the players control the economy,. They'll eventually have standard buying/selling prices for things.
Then the emergent prices could mash with the gameplay rules that are set in stone, thus generating too much frustration and making the game not fun.
For example a very important item could become too costly due to an unbalanced rarity, forcing players to repetitive work to obtain them.
Or something vital to some class could become worthless, and who chosen that class in the first place finds himself underpowered.
Games have to be fun, and real economy isn't... some (or many) directions are needed to avoid exploiting and frustration, imo.
Or you could base your entire economy around treachery and backstabbing like in EVE.