Replying per Jay's request...
I had a basically stock ZRX-1100. I did re-jet it (OMG what a difference that made) and add a bunch of farkles. It was a fun bike with a lot of grunt while being affordable and insurance friendly. A retro-like sport bike but with much better position. There are several reasons I left it for the Concours:
1) The carbs were just screwed. I suspect the f'ing ethanol they started putting in the fuel. My race mechanic friend and I spent many hours on it trying to get a reliable fix. Nope. Then I took it to two shops, multiple times. They either could not fix it or it would be "fixed" and then "break" again a few months later. I swore I would NEVER own another carb vehicle.
2) Regardless of the windshield and how much electric clothing I wore, I would FREEZE TO DEATH on the bike at any temp below something like 58 degrees. The bike was great in the summer, though.
3) Like my previous bike, I got sick to death of constantly cleaning, oiling, adjusting, and replacing the chain.
4) I wanted more storage, more electronics, and generally more modern.
5) It was getting old and the black paint was coming off and the alum was corroding and pitting.
Looks like he bumped the displacement, which would be even more fun. Of course, there is the risk that it wasn't done right, or that it would lower the life or cause problems.
I have absolutely no idea what it would be worth, especially without seeing and riding it.
Why are you looking at it?