I'd make a $500 offer.... Otoh, if it's what works for you, in perfect condition, maybe a $750 max. But at 7 years old, even with only 50 miles on it, it's not in perfect condition. The tire rubber has aged, so you're not going to get max mileage from them any more, not even if it was kept inside for those 7 years....

Just my 2 cents worth. YMMV.