About 3 years ago I had to deal with a counterfeit item bought on ebay. In such cases an experienced seller usually offer full refund no questions asked, this is the best policy and saves time and the item, though the seller loses shipping charges they paid when the item was initially shipped and the buyer has to pay the return shipping, sometimes to make the buyer happy, seller even offer to pay return shipping. These small loses are usually considered as "cost of doing business on internet".

Paypal use to require the buyer to prove that the "assumed" fake item is actually fake. In my case Paypal asked me to obtain a certificate either from the original brand or some authorized dealer. If I would have gone that route I had to pay for appraisal fees and spend time shipping/taking item to the authorized dealer. I guess this was Paypal's measure against every other buyer crying fake when they start feeling buyers remorse.

I hope Paypal has not changed their policy of asking for the counterfeit certificate, making it too easy for buyers to claim fake items.