Well, you need to answer some questions yourself before you know what it is worth.
With these early K0s the serial number is important, for example, non sandcast bikes can share a lot of the same rare, hard to find parts as sandcasts. Get the serial number, for the frame, AND the engine.
*HOW* does it run. I have bought pieces of crap and had them running in a few hours, that did not mean that they were ready to ride or even ran well. I saw no mention of MILEAGE, there is a big difference in price for 10k and 70k miles just like any other vehicle!
You can get a bit of a premium for a K0 over other models, with all factors being equal. I've seen RESTORED K0s go up to 14.5k but that was fully restored. Total teardown, repaint, polishing, rechroming, and a NOS parts laundry list longer than this response. If you were to buy all the parts you needed to restore the bike pictured NOS you would be lucky to break even.
If it were a sandcast all bets would be off and it would be worth the 6k easy. Since it is not, it is probably arguable about whether it is worth 2k. It is hard to tell from your story and the pictures, there is a lot that is unseen and unheard. It all depends on the condition of this stuff. Parts may look good but when you gotta put the part up on ebay and disclose every dent, scratch, and imperfection you start to realize you don't have something that is going to fetch a premium like you've seen on ebay maybe.
Summary: Insufficient info. Estimate: 1k-1.5k