Mileage, if it really is accident free.
I've seen two or three that cheap as well that appear to be not a scam. Maybe not the best examples, but yes if you're patient and willing to travel (or lucky, or don't care about prior crash damage) you could get an 86 in your driveway for $15k nowadays.
http://www.libertyautocity.com/used/...d1ce98a09d.htm
http://www.cars.com/vehicledetail/de...6095/overview/
http://www.cars.com/vehicledetail/de...9553/overview/
http://www.cars.com/vehicledetail/de...3288/overview/
Personally, I'd save up an extra few thousand and get a nicer one.