Depends alot on the rust. Looks like some on the RR 1/4 panel. The fact that its a vert should add a grand to it. You know what they say "if the top goes down the price goes up".
Also depends on the cars location. Looks like a Virginia plate to me, so East Coast will be "worth" more because there are fewer of them. Here in Northern Michigan, the owner would be asking about 10K for that car. Depending on the floor, trunk and extent of quarter rust, I'd say anywhere from 5K to 7K, but that's just me...