A decent seller on
Ebay
would not do that, only the shady characters trying to wriggle out of their resposibilities. Anyone who did that to me and made me wait for the longwinded resolution process would get appropriate feedback left.
Ok, the buyer may be a chancer, but if the item is returned and there's nothing wrong with it, he'll have to pay his own postage and lose out, and you get the item back to resell. If it's faulty on return and there is no evidence of it being done by the buyer, you take the hit and refund.