I'm a big fan of both Midwest Photo and KEH. Personally, I don't find the prices at KEH objectionable, especially if you consider the quality of service and conservative grading of their items. Everything I have ever purchased from KEH was in better condition than I had expected and none of it has ever let me down. When I switched medium format systems this spring (to one that would meet Ohio University's requirements, grrr....), I bought everything from KEH and I'm very glad I did. I bought an RB67 Pro-S body, 120 back, NPC Polaroid back, KL 127mm, KL 250mm, and 50mm C lenses. Granted, I dropped a fair amount of money on this setup, but I still saved roughly 50% compared to what I would have paid new, and most things (the body being the one exception, got it in bargain condition) are in practically new condition. Even when I decided that the 50mm C was far too soft (just a dog of a lens in general, from what I understand) and returned it for a KL 65mm, the service was excellent to say the least. No, I'm not in any way affiliated with KEH, just a satisfied customer. I've purchased probably 70% of my equipment in the last 5 years from KEH and haven't been disappointed once.

Midwest Photo is also a great place, especially if you can make it to their store on High Street in Columbus, OH. Good service, friendly people,competitive pricing. It's easiest usually to just call them when you want to make a purchase instead of looking at print ads or on their web site to check what they have laying around.

As for eBay, I think that as long as you're careful, pay attention, and stick to sellers with good feedback, you're generally safe. Just don't do what I've done a few times and buy stuff at random because it looks like something fun to play with (anyone want to buy a 75mm f/1.9 in Ilex shutter?). I've had pretty good luck in general, and I think as long as you play it safe, it can be a pretty reliable and less expensive way of purchasing gear.