but ebays terms state that sellers aren't allowed to sell counterfeit products at all, so isn't how they advertised the product insignificant?
The point is you are not the copyright police, you worry about yourself and let eBay worry about eBay. Doing more [what, out of foolish pride or revenge?] is foolish. If you are in a septic tank stirring things up will get you in a mess in a hurry.