You are selling stuff in droves to adventurers that they don't do anything with appearantly. It is tedious to manage the equipment of 10+ adventurers especially since it breaks all the time. If a customer wants to buy an item that is more powerful than the one they are using currently there could be an option to donate that item to them for them to use in quests.
 "Shop Heroes"){kind=icon}
 "Gun Disassembly"){kind=icon}