I am not saying my luck is typical, but I have bought 3 generators from GL.
A low hour 125KW Onan Civilian model for work, $4,000 needed simple repair to get running (replaced engine control circuit board $300 , and clean some ground points) typical cost for same model in similar condition off ebay, etc. is about $12,000
The second was a 3,300 hour skid mounted 30 KW Kohler civilian model for $1,200, no muffler was included, the exhaust had been removed and taped over while it storage the tape/plastic had rotted away allowing water into the engine, it was lightly seized when I bought it, thankfully soaking for a few days in marvel mystery oil and Transmission Fluid freed it up and it now runs good other than a couple of minor issues (needed new battery (missing), new battery cables( crushed in storage) battery meter broken, local run/start switch does not always make contact, could be replaced for $80). Now in use as backup unit at my mother's house (all electric house, with well pump, etc.)
And most recently 900 hour 3kw MEP-701a/016B for backup at my house at about $450, dead 24V battery ($70 or so) , slight oil leak from oil cooler ($40 on ebay, bought one, but have not bothered to replace yet). No other problems, added oil, fuel, and jump started it from a pair of 12V batteries in series to make 24V within half an hour of pick up.
The trick is to look at the photos for any sign of missing parts, or damage and not bid too much, know there will be another along in a few weeks if the price goes too high.
Ike
p.s. on other electronic items, I bought an HP-9000HDN color laser printer that sold new 2 years ago for $13,000 for $250 from GL, only needed black toner/drum to get running. Only other problem is the bulk paper tray always shows full even when empty.