Does eBay charge me for refunding an item?

I sold an item on ebay for $300 dollars and I sent it Priority+ tracking+ signature confirmation. USPS lost the item. Am I responsible as the seller to give a refund? The tracking says "out for delivery" but not received. I am willing to give a refund for the item but I was also wondering, if I refund the money, will ebay still charge me for service and listing fees? Thanks