eBay is a hotbed for scammers selling junk or just flat out ripping people off. I'd estimate somewhere approaching 30% of all the stuff on there is just garbage people are trying to offload. Another significant amount of transactions (2-5%?) are plain old fraud. Why do you think they have the prominent Paypal protection notices? Yeah, there's great deals available, but you gotta be careful!
Two things: 1) Never deal outside the auction. If you do, eBay/Paypal protection will not apply. 2) Never return it 1st - file the claim for not as decribed 1st. They'll just ask you to return it anyway, but you have to get the claim established first.
I've had attemped rip-offs a few times and always eventually got my money refunded. One time I bought a driveshaft from some wanker who told Paypal he did not even want it back. Kinda proved the point, I guess - junk!