Seems to Ebay is the first outlet for goods where no-one really has to prove the worth of the product. Particularly when having problem with a Seller who seemingly has no desire to respond or rectify your complaint. Final result from Ebay support, when they invariably are unable to get the seller to do anything at all, is for them the pass the 'buck' on to Paypal; where even Paypal if the find in your favour, the Buyer has the added insult of having top pay for the return of the item.
The best way to deal with an errant Ebay seller, and there are many of them, is via the Small Claims Count Court, this action alway works but one problem, if the Seller hasn't given you his address details, when things are going sweet, Ebay wont help you there either. Otherwise your stuck with faulty goods. I've a few negative feedback comments against my profile, only because these errant Sellers hate the light..
Oh yes, even though Ebay may agree the Seller has defaulted on Ebay Terms and Conditions, if his 'track' record has earned them enough funds, Ebay wont do anything to help you except again to 'pass the 'buck' onto Paypal, of whom they own.