forgot decimal $802.00 vs $8.02

I placed an AS bid for what I thought was $8.02. When I checked my wins I noticed I entered $802.00, obviously I won the auction for $17.50 + 7.00 shipping. ($24.50 for a $20 item). I sent the seller this email.. I won the auction referenced above. However, I did not plan on bidding the winning amount of $17.50. I attached my Auction Sniper bid page to show my bid was entered as $802 instead of $8.02. If I win more of your auctions for the same item with combined shipping I would like to follow through on this transaction. If not, I would prefer to have my bid cancelled. I do understand it was my error and I do not want to jeopardize my feedback rating or risk a NPB complaint with eBay. Let know if you want to wait & see if I win more of your auctions, cancel my bid, or make me pay for this one. The ball is in your court. Here is his reply..I'm sorry to hear of your problem, however, we will have to hold you responsible for the auction you won. There are several checkpoints that can be used before the auction ended to retact your bid. Bids can not be retracted after an auction ends. You may see if you win additional auctions, however, payment is due for this auction within 10 days of auction ending, thank you. My question is could'nt the seller have cancelled my bid even after the auction ended? I did pay after receiving his email and learned to be more careful. However accidents do happen and I would hope sellers would be a little more understanding. Oh well.