That's why it always annoys me when gamers think that "realistic economies" (in games outside of the 4X/political sim genres) are a great idea. They don't understand that only way that the player character can meaningfully progress in a game economy is if it's built specifically to allow them to do that. Bolting on an imitation of supply and demand to shops doesn't actually make the game more realistic and it usually doesn't add anything interesting to the game.

Then you get to "player-driven economies" in MMOs, which require constant developer intervention to avoid devolving to the point where most people don't have any economic power. You'd think that gamers would learn something about capitalism from that, but no such luck.