Unless you put in a price that was above his asking price? Wouldn't you get some money back then? In some instances this will happen, yes. If you think about it though, in your example, the transaction will not work. no, if: he tries to sell for 1k gp and then you offer 2k he just gets 2k [a] offers to sell coal for 1k gp offers to buy coal for 2k gp after [a]'s offer get coal and 1k gp back, while [a] gets 1k gp