A trading system would really work well but this happens very frequently:

person: "Give me 20k for my kiwi blade"
newb: "OK HW I DO?"
person: -explains how to trade-
newb: -puts in money and presses "accept" and confirms-
person: -presses accept and confirms without putting up an item-
newb: "WERE KNIFE"
person: "BYE!" -unsticks-
newb: -sadface-