Multiple factors involved. How much you are will to pay, how much the seller is willing to loose, location, demand, your negotiating skills, and so on.
NADA and others are a very rough guide concerning pre-owned but you can use them as what your home state may charge you if you live in an area with personal property taxes. Insurance and banks will uses the published guide to determined value. Sounds like a real find if you can get what you want concerning price. You'll have a hard time moving into something better.