Excellent point. Looking at parts availability, I can see some of that. Unfortunately, I'm in the same boat with my 350, and I don't see many 600cc bikes that run and ride well for this price.
This bike comes with a nicely loaded out box of spare parts, and the owner has made a couple of modifications replacing some of the hard to find parts with more common stuff. He used the bike to build and test fuel injection systems for the FZR, which he would then sell. This particular model looks a bit rough. If I didn't know the owner, I wouldn't touch this thing with a 10' pole. The body panels are mismatched and kind of beaten up the thing was painted in a couple of gawdawful color schemes that when all was said and done, nothing matched. It was laid down before he bought it. However, he maintains things impeccably. Any mechanical damge has been properly repaired. It runs well and everything related to how it rides and it's safety is in excellent condition. It comes with plastics to replace the cracked and scratched parts, and he daily rode the thing over the summer.
I'll need to do some work to make it look nice, but I have a friend that does a good job with paint that I can usually trade labor and car parts with to help me out. Mechanically I am confident in it, and I don't see anything on the bike that I don't have the tools to handle. And at least initially, I'll be keeping the Honda as a backup/parts chaser while I finish making it nice enough to sell for a decent price- likely enough recoup my initial investment in the Yamaha.