Depends if it has ALL the original components, if it does then yes it seems to be a fair price from what I can tell from the photos. There does appear to be some degree of rust on various areas, the springs on the brake calipers for example, those could snap if the rust is too bad at some point. You can get most, if not all, the original components on E-bay as needed. If you decide to upgrade components at least save the original stuff so the bike can be brought back to it's former vintage value if need be. I think the front gear rings may be worn out because some appear to be pointy in the photos. It looks like you might have your work cut out for you getting this restored but excellent condition ones sell for around $700 (in blue, the least valuable color, orange and yellow are the rarest so those sell for more) so you have room to play with.

That bike was the premier touring bike made by any company back in the day, so it was a very highly thought of bike. If you do decide to go touring on it some day buy a stainless steel rear rack and not a cheap aluminum one because the old metal technology back then did make touring bikes in general flex a lot when loaded and going down a hill where the speed may go above 15 mph those frames would visually flex back and forth, and a solid rack will help reinforce the rear.

If the bike fits you then I would offer $250 and see what the seller does, if he ok's the offer then ask if he has any other tools, parts, and accessories to go with the bike.