id say that the fee is more then likely the fee for placing the bike/part up for auction, finishing the transaction and not going through disputes with ebay. If you go via disputes you wouldnt have had to have paid but seeing your DH placed the item back up forsale instead of waiting ebay then thinks that the transaction is complete and that its a second same item...KWIM.

I would defently be contacting them and telling them about the transaction....but again i really think that the $$$ fee is the initial fee for placing the item up for sale in the first place not for selling the item

good luck