I would not pay that much for a 3,600 RPM "advertised 6.5 kW" no name generator, with unknown hours. $200, is the most I would give if I wanted one.
I have personal experience with a 3,600 RPM diesel generator, what a POS. Would not start in cold weather and obnoxiously loud and vibrated a lot. It was a "Coleman 4 kW diesel generator" sold by WINCO. With a Lombardini diesel engine.
I wonder if "auction folks" are telling the truth about their past prices.
i