The seller accounts for the last 25 years of the tractor's 47 year life. 250 hours in the first 22 years is extremely rare but might be possible. Inspecting the drawbar, pedals, steering, shifters, clutch free play, paint, hour meter and seat suspention should tell if it has 350 total hours or 350 hours since the tach was replaced. It looks like it has an alternator instead of a generator.
If the 730 is in good condition with maybe 5000 hours and the engine has never been touched instead of completely rebuilt, $3000 may not be an unreasonable asking price. It might sell for $2500+?