I personally wouldn't ask for anymore than I originally quoted, if it was my mistake, then my loss. If I gave someone an estimate to paint their vehicle and ran in to something I might have overlooked I would never charge extra. I would see it as my fault for overlooking it. Not everyone operates under this principle and their are many out there who would fight you tooth and nail over extra charges. I also agree that you should wait to see if it gets delivered and I'd also withhold feedback until he leaves his. You have the listing to prove you did no wrong. He is 100% at fault if he misquoted the shipping costs, especially if his feedback rating shows he has shipped several items.