If the bike only needs tires, I'd say it's not a bad deal - I picked-up a very similar GP (same color, also very tall) from the trash during the summer. In addition to tires it needs wheels, a seat, and probably cables, brake pads, and other related small bits. I've got those things in my garage, but if you had to buy them I think you'd be hard pressed to get them all for less than $30.
I had another GP which I traded away last year as it was a bit small for me, but I'd say it's a good ride for commuting and recreational uses.
I'm in central CT and would say that the price is very fair for the area - I watch Craig's List pretty closely, and don't see many bikes of comparable caliber priced any lower than this.