We just purchased a new Sony 46 inch Z4100 Series LCD television and are looking for Monster Cables, either the Ultra1000 or M1000 Series to compliment the connections.  I enquired with Monster Cable Customer Service and they advised me that they were aware that fake cables (probably from China) were being sold on Ebay.  I emailed seven of the more prominent sellers of Monster Cables on Ebay and asked the question....."Can you confirm that the cables you are selling are authentic Monster Cables manufactured to the standard of quality specified by Monster Cable USA and not substandard knock-offs or what is known commonly as "B" grade items?"

Four replied in the affirmative and I am still waiting for three of the sellers to respond.  I am surprised that PayPal wouldn't do anything for your as I had one incident of the seller misrepresenting the item (not cablese) and I received a complete refund very quickly.  But make sure you cover your butt too.  Email the merchant and confirm that the item is authentic and is what you think you are purchasing.  If the merchant lies, he is misrepresenting the goods and you have an action to pursue.

Another approach to use is to purchase with a credit card and if the item is not what you ordered, notify the credit card customer service and refuse to pay for that item.  Some credit cards will go to bat for you; others won't.  If you aren't sure if your credit card will support you, don't use that card to purchase the item.   

To a great degree, it is buyer beware but I've found some excellent prices on Ebay, but then, I do my homework.