I sold a bag on eBay to an ebayer who happens to be the only bidder. The ebayer asked if she can get a copy of the receipt if she wins, and of course I said sure, no problem. The shipping cost was very clear on the auction, but after bidding last minute and winning the auction, I sent her a Paypal invoice, she then asks if I can fix the shipping cost from $18 to $8. Should I? I mean I'm not trying to cheat anyone from the shipping cost. It was clearly stated on my auction. This bag is pretty large, so I think it's reasonable. The last bag I sold, I actually paid more for shipping ($6 more) than I had charged for (b/c of the weight). Still I always keep it under $20. What do you guys think?