Selling on eBay, selling *anything* on eBay, is plain stupid unless you have so a high volume to cover the inevitable losses you will get.
If you sell rarely, variance might kill you, like it did here.
Just out of curiosity: did you know about the risks involved and you did it anyway, of somehow you managed to elude this quite pervasive information?
Actually, no.
I was sucked into the profits like many other naive sellers, only to "learn" the cost of selling BTC on eBay later. Money has an effect on all of us.
I'm pretty sure paypal doesn't allow anyone to sell BTC on ebay anyways. This was your fault, if this was an item allowed to sell by ebay, you could just contact their support. I don't get it, the ebay listing is 10 BTC, and you tried to sell someone 16 BTC. So you have 16 BTC, the least. $400 USD was lost by paypal fees, don't you have almost 10 BTC left?