Yep, me (the other Gordon) - I've been watching Z1 znd KZ's sell on EBay every night for a long time. I've tracked them by adding every original, non modified bike to my watch list so I could follow the auctions through their entire bid cycle - have done this for many, many months now. I also track H2/Mach IV's and since I'm now looking for an all-original, low-mile 1974 Suzuki GT750 for my collection, I could give you the averages of the last 30 GT750's sold. IT's all about doing the research and having an interest in what you're collecting.
The $2,000~2,500 pegs the KZ100's probable re-sale value. What's it worth as a commuter - probably could get a newer, shaft-drive and water-cooled bike of newer vintage for the same money. You are going to have to find someone who really wants a KZ1000 because they had one years ago to get more than that.
I bought this 900 in February for $3,500 - this was my 12th Kawasaki. I knew this one had potential since it was 95% complete, 18,000 miles, within driving distance, and ran. I had done my research..........
Regards,
Gordon