Incredibly stupid thought. Would heavier taxes prevent undercutting? Like lets say you put a stack of items on the market board that has a market value of lets say 100gil, and someone puts a new item for 50gil. That 50gil item would be taxed heavily, leading to an end price of maybe 150 gil that the purchaser has to pay, and only a 50 gil profit for the crafter.

I am a computer scientist, i don't pretend to fathom how economics work, but from an outside looking in perspective, wouldn't this solve the undercutting issue?

(Though I'm still a fan of removing all items after 10-15 from NPC vendors)