I currently own two GV250's and sold my first one last year, for a total of three. The one you pictured seems like it's been cared for so yes, I think it's a fair price. Make sure the mirrors retract as they are scarce as hen's teeth. My favorite GV has 20,000 miles on it and shows no decrease in power or reliability. If you want to add a rear trunk it's a simple matter of bolting a piece of plywood to the aluminum rear carrier and then bolting the mounting bracket of the box to the plywood. That way you can buy a box on ebay for around 50-60 dollars. I removed the lumbar support so I can sit back further, which seems to be a common complaint of the GV250. I love the maneuverability, adequate power and 70 mpg. I find it runs fine on regular, not needing premium. I also added a loud horn and ran a 14 gauge wire to the phone charger socket so I can power an air pump or charge the battery via the socket.
