Hi .. Ebay charges final value fee unless action is taken to recover.
If buyer wins and doesn't respond , an unpaid item dispute should be opened..
http://pages.ebay.ca/help/sell/unpaid-items.html
Unpaid, close after 4 days and ebay credits fee. Buyer receives a strike against their account and cannot leave feedback.
Cancelling a transaction at buyer's request will also recover fee..
http://pages.ebay.ca/help/sell/cancel-transaction-process.html
Unpaid buyers should be added to your blocked bidder list and buyer requirements should be set to block any bidder with 2+ strikes on their account..
http://pages.ebay.ca/help/sell/manage_bidders_ov.html