Greetings! Nice bike, not in too bad of shape, don’t see too much rust, looks like it’ll clean up with some elbow grease.
$1500 does seem pretty steep though for not running and been sitting. I picked mine up a couple years ago down in San Diego for $1300, no title, was told it had been sitting since ‘97 according to the tags but was able to see it running, rough and not rideable, but running. People tell me I paid too much for an old bike and I’ve put almost 1k into it but I’m happy with it. It leaks oil, not the greatest clutch/shifting, revs out on the freeway, not the best handling(could probably use new tires and steering bearings), but it has character and I always have a smile at the end of each ride, and I enjoy working on it.
I would say $750 max, maybe 1k if I had the money laying around. Looks like at the least new battery, rebuild both brakes, new tires, oil/filters, air filters, carb clean clean clean, and possible charging system, mine was toast.
Check the oil, and turn the motor over slowly, if it feels normal give it some good kicks to feel compression, and if the bike rolls try shifting through the gears. Take a peak under the gas tank for thick rust spots/leaks. And inspect the wiring for any hackery.
Good luck!