I bought a bunch of flies off eBay but stopped that after about 10 purchases. As Adrian and Mark said, you get what you pay for. A bunch of the cheap flies I bought off eBay looked ok when I got them, but ended up coming apart before I ever used them! They looked ok when I got them so I left positive feedback, but they didn't hold up. So I wouldn't exactly trust the feedback system entirely. You don't know how well a fly is really going to do until you fish it, and most of the time the feedback you see is left when the person gets the flies and before they ever get a chance to use them.
I'll stick to buying my flies at my local shop from now on. Cheaper flies aren't really cheaper if they fall apart...
My passion for catching fish is eclipsed only by the fish's passion not to be caught.