unfortunately man; the seller will always loose
you can try to argue, but PayPal or eBay won't care. Your best bet is ask buyer to pay shipping, return jeans to you for full refund.. and try to sell jeans again. Most of the time buyer will not pay return shipping, and since you do not get the jeans back you cannot issue refund. so that's done.
this is one of the risks w/ selling on eBay.. buyer always wins. well from my experience anyway.