There ARE some good eBay parts...you need to know what you're buying and also take into account what the item actually is.
Example, I buy a lot of LEDs for projects on ebay and they work fine. I would NEVER EVER buy an eBay $150 turbo, though. I'd not even take it if it was free!
Daily: Audi S4 b5 | Project: Turbo ZX3
LED Conversions | Vinyl Carbon Wrapping | Powdercoated Valve Covers