Posted By:
boxingcardmanThen in court you can prove your case, he can prove his and you end up with a net $800.
If that doesn't sound appealing/feasible, follow the Golden Rule...cancel the sale with an explanation and refund the money or close the deal and forget about it. It's the only way to address situations like this in life. Otherwise, you open the door to all sorts of crap that isn't worth the time or the stomach acid.
Of course, you could also put a big, honking crease down the middle of the card before you ship it; odds are he wouldn't even notice