I refunded money to buyer who changed his mind and relisted and sold item again. Do I have to pay ebay fees twice?
You need to send the buyer one of these:
http://pages.ebay.co.uk/help/sell/cancel-transaction-process.html
Tell them it's coming, and that it wont effect their a/c.
If they don't agree you wont get your fees back.
unless you cancelled the transaction then yes you pay the fees twice. How do ebay know otherwise.