It's not like you have infinite hats in your inventory. Also, that money they get from refunding the hats would probably be put torward uploading customs (Which cost 1,000, 2,500, 10,000 and 20,000) or buying new hats which are a lot so don't think that money is gonna keep piling up because it won't. People will spend all of it sooner or later so don't think Graal will lose business from this. Think about the new players who don't have as many hats as old players. They won't have much to sell.