Caveat emptor ... wherever one purchases from. Whether Amazon, eBay, the local flea market, a face-to-face seller, a shop, or whatever.

Thankfully, I tend to be fairly detail oriented and take my time when evaluating an item for purchase. I want the details and specs, and I want to compare to others, and most particularly to compare against the manufacturer's published specs on the thing. Helps weed out some of the riff-raff. Can't recall but a handful of times in the past 20 years where I've missed something and instead got sent an item that was merely a compatible thing and not the real thing itself. This sort of thing used to be relatively rare, but with the rise of global-sourcing sellers it's become much more prevalent to find everything including the thing you're really looking for. IMO, not much different than Joe's Local Shop, really, except for scale.