His prices on something like a random atlantic 45 are based on people buying them as collection fillers, etc., as most random atlantic 45s should probably really be $1 but nothing on his site is $1. You can still find some sellers on Gemm as a better source for things like that. It's fair game for him to do that, though, he has enough stock that he can price stuff at a premium and still make money off of people looking for a specific item (rather than just generally buying).
I did actually have a bad experience recently, I saw he had ocie iii on CIM with the flip on his website for like $20. I had never seen it with the flip before and I bought it as a random chicago title. He emails me saying they can't find it. 6 months later it shows up on their auction. That was pretty lame I thought. I didn't know it would go for $500 either, I just bought it (or at least tried to buy it) because I hadn't seen it before. Did they really lose it and then find it later and just decide to auction it?
Also, the person doing their auctions is very unknowledgable and lists total garbage, misinformation, the wrong sides (or has audio clips only of the bad sides, or the audio clip cuts off before the chorus and you can't tell if there's a group), etc. At this point they seem to have built up a following of people specifically looking for the types of things they auction (e.g. "boogie" records, etc.), but I think they alienate a lot of real collectors with their listings, and it's always amusing when there are common records or just terrible records listed that get no bids. They had a bootleg of linda jones 'hypnotized' up recently with a different artist on the flip, description was something like 'rare one for her', I emailed them saying that it was a bootleg and they took it down. How could anyone who knows anything about soul music think that hynotized is the 'rare' record by linda jones?