If you stated in the auction that it was sold as-is, then I see no problem not refunding anything at all, but since you answered a question making the asker think that you were giving a DOA (which you were not) you should expect to at least get a negative feedback.
Noone can think, that it's ok to get an item repaired WITHOUT agreement with the seller, and then expect anything from the seller.
If they have paid 260 USD for repair, then ask for a receipt and the place where it got repaired. Phone the repair place and ask.
Personally I think it sounds like someone that just want's to get the price cut down, by pulling a scam on you.
