I just bought a set of Apex Plus irons this morning. They looked practically brand new, and they were only $79+tax. So far, I've only hit them off a mat in the store --- I can't wait to try them out on the course.
I also play Hogan BH-5s. They're game-improvement (at least, I think that's the right category for them), and I like them quite a bit --- though I think they are a bit less forgiving than some other clubs I hit.
When I got into golf (almost exactly two years ago), my father-in-law said to read "5 Lessons", and my uncle (a scratch player before breaking his back) said he liked Hogan stuff. So, I decided to put together a completely Hogan bag since, as the OP points out, you can find the stuff fairly cheap online.
My take on the cheapness is:
1) Since the company isn't really around anymore, they don't have anything 'new' and everyone seems to want the 'new' stuff. The market dictates that 'old' stuff is devalued --- cheap.
2) It's been several years (since 2007?) since people could buy it 'new', and they've been trading in the clubs for the next set, so the market is getting a lot of Hogan stuff. And traded-in clubs usually go for cheap.
All the reviews I can find seem very complimentary of the Hogan clubs --- even the older reviews from when the company was around.