Minecraft wiki entry for Trading, associated text: The first factor is demand. An item that was sold out gets a price increase for all players when resupplied. If a player does not trade for a higher-priced item, the price is reduced the next time the villager resupplies. Demand is tracked per item, not per villager, so a villager can offer a higher-priced trade for a single item while other items are cheaper. Trades that have a price multiplier of 0 are not affected by demand.