the dealer
Notably Dangerous Demo-Knight
They take approximately 1/7 of everything you make. That's like 15%. Who the fuck charges that much for "fees"? Especially when many of the items come from their store already, meaning they already made a lot of money just from putting the items in circulation. Something more reasonable would be like 3%. This is making it extremely hard to make money on the Community Market from arbitrage, unless someone sells an item for extremely cheap.