You can not stop this but you can slow it down. File a dispute with paypal even if the seller refunds the money. Also file complaints with Ebay and make sure to leave negative feedback and 1 star across the board. This will eventually shut their account down until they get up and running under a different name. Even after they are back under a different name at least the feedback on the other account will alert others to the problem in general. You can also send the links to Ebay customer service and they will investigate the products.
The biggest issue is that many times amateurs don't even realize they have bought a counterfeit. They counterfeit many mics and headphones and get away with it a lot of the time because the product does work. Someone that can not compare to the real thing is liable to believe it is a legit product. When someone complains they immediately refund the money to avoid complaints and bad feedback so the can keep the operation running.
It's just very unfortunate overall.