Better stock for villagers

Viilagers should have stock, but not like normal.

So lets say you need to trade 9 wheat to unlock a hay bale trade and the more wheat you trade to that villager, the lower the emerald price will be on the hay bale trade, but only for a few trades because then there will be low stock! If you don't trade with villagers then demand will go down, causing prices to go up and down depending on the demand (Demand will go up if you trade a lot, even if you're not trading stock.)