Yeah, compared to civilian diesel continuous duty gennies, they're a great deal even at today's closing prices...provided they work. The reason they don't sell for their street value as running condition is that you have no idea what's under the hood and get no guarantees that your money's not going to be wasted. A reseller can ask much more because you can go see it run with them, much less risk involved.
I bought a 5kw a few months ago that turns out great for storing a tarp on, but it's junk as a generator. In the auction, it looked like it would be fine. Cash I won't get back...
Also, the hour meters don't really mean anything unless you have the maintenance records, or you're reselling it and want to have plausible deniability. Units can get a full rebuild and be like new without getting their 3000hr meter changed, while heavily used units can have their meter fail and get a new one swapped in. It's primarily for maintenance interval tracking rather than machine life. I have machines at work that have 20 years of service and had the hour meters replaced several times. A new meter starts at 0... I could sell you a really worn out machine with 10 hours on it...