yeah, you could probably get a similar vintage ninja running for the same price.
That being said, carb work isn’t that bad, if that’s the real problem. I would take $800 or $850 and be like “I have cash, bike doesn’t run. Take it or leave it”. Jets are like $5 a piece and whole carb rebuild kits aren’t much usually. Look to see if you can find the pilot air screw or the cover for the screw. Usually brass with a tiny hole in it. It could be that he just didn’t know what he was doing when he replaced the jets and didn’t change the amount of air / fuel the carb was getting. Real easy fix.
I think that Don guy who races, from Latrobe (name might be eurodad) on here, is pretty good with carbs so hit him up. I think there was a thread in the off-road bikes section that he was posting in.
chris