Desirability determines demand. Rarity determines supply (relative to the entire value on the market). Both are taken into account to determine the price. My

Desirability determines demand. Rarity determines supply (relative to the entire value on the market). Both are taken into account to determine the price. My favorite place to view this is Path of Exile in game economy. They do have random loot boxes for cosmetics, but I'm talking about the actual in game economy around items that power up your character. None of which can be bought for real money and instead require time to farm them (RMT does exist but is against ToS and can get you banned). There are extremely rare items that cost nothing because they aren't used. There are quite common items that have decent value because of how high the demand it. Technically the game doesn't even have a currency, but players found a small set of common but also highly useful items that have become the defacto currency so much so the developers even admit they now count as currency.