I think it's a deal of you offering to trade something plus something more, cash ammo etc. so they can get a better deal out of it. May as well trade up and get more, who knows maybe a bidding war will happen and you can get more than what you were asking for.
But honestly I have done some offers and had it work out fine. If something has sat for a week or two with little to no interest and you offer 5 to 10 percent less than their asking price a lot of people will jump on it. For me to buy something it either has to be a good value or something I really want. If you are selling an item for retail and it sits you either have to be prepared to wait a while or take less than your asking price.
But honestly I have done some offers and had it work out fine. If something has sat for a week or two with little to no interest and you offer 5 to 10 percent less than their asking price a lot of people will jump on it. For me to buy something it either has to be a good value or something I really want. If you are selling an item for retail and it sits you either have to be prepared to wait a while or take less than your asking price.