If you check this link you will be able to see how many sales you have lost.

http://offer.ebay.com.au/ws/eBayISAPI.dll?BuyerRequirementsActivityLog

I have only lost 5 sales but those buyers could have been wanting to buy much more, that also assumes that that part of ebay actually works.

If you have sold an item allready to them I would just send them a paypal invoice.