Whether I'm buying or selling the lower priced rolling stock and scenery items usually sell at the sticker price. The higher price items like engines are usually negotiated. I try to price low as I am never selling my old items for profit, just looking to recover some cost and make room but I always leave a little wiggle room for negotiation.
When A customer makes a RIDICULOUS LOW OFFER, I just say thanks your not in my price range and move on. most of the time these low ballers just move on