Fun thought: since eBay often rules in favor of buyers, it would be fun if someone would 'abuse' this: buy a good # of often-faked parts from all sellers that offer them, test extensively, and open disputes for any fakes received. That should (in theory) cause a good deal of $ losses for any seller that sold fakes.
Maybe repeat regularly, and it might remove some fakes from the market?
Back when everyone was making Windows 8 tablets with a quad-core Atom and a $350 price tag, I ordered one of theirs. It got good reviews in the Maximum PC comparo of the time, and it was available with a then-cavernous 64Gb of flash.
In week 1 the Wi-fi wouldn't keep connection. By week 2 it had fully bricked. I initiated the RMA process, and the chat monkey asked "If we refund you $50, would you keep the device?"
I ended up getting the Asus version which had a nifty little clip-on keyboard, and it at least lasted the warranty term before the touchscreen cracked.
I did end up getting a partial refund for about the price of a replacement OLED screen.
Also, there's this interesting exchange I had with an eBay seller a couple of years ago. I purchased a bunch of NiMH batteries. Because I test every component I buy even for my hobby projects, I immediately noticed that they were 1/10th the capacity that they should have been, and were marked as.
I contacted the seller to return them and get a refund. They told me "honest mistake" and then began a negotiation. "How large of a refund would you accept?"
Since the batteries were useless to me, I said "100%". In the end, I did get a complete refund and didn't need to return the batteries.