Normally most GPU's are made in Taiwan/ mainland china.
AMD/NVIDIA just make the reference design of the video cards, then they ship those references designes to companies like XFX who then create their own version (either with a better cooling solution than the stock reference design, or just keep it and slap their logo on it).
The intial start-up of a GPU counterfeiting operation wouldn't be economically viable as there would be a tremendous amount of overhead i.e. very low profit margin....BTW...e-bay sux...buy your parts new.That goes for all parts: cars, computers, any type of item really they are all manufactures seconds or some overused pos someone is trying to pawn off as in great condition...All of the auction sites used to be great until rip-offs, scams, and idiots ruined it..P.T. Barnum was a genius as quoted: "There is a sucker born every minute".