Gurdon
20% discount is a lot, he can buy things for 80% of the price and sell at 90/95%, then he can have 15 to 20% profit. and everyone else was going to buy it because it's cheaper than the npc's shop. This is an easy way to earn a lot of money, he just needs a little initial capital and after some time he can already outsource almost the entire business, he goes once a day/week to the npc's shop, buys a lot of items ( consumables are always in high demand), after all it's up to a player to do the work of selling to him, and just enjoy the profit. he can create a contract with some player and give him a small % of the profit in exchange, so he can earn money consistently and with little effort.