I'd say, if it has good tires, runs and starts well (check the spark plugs if you go take a look), the sprockets and chain are in good shape and the brakes don't need replacement, a fair price point would be 850 dollars. As dave said, those pipes will sound a bit ridiculous most likely, and with the stuff already missing the price drops. A mint condition, stock bike will go for 1100-1300 I'd say.
anything that's not good on it, will reduce the price by its cost (excl labor costs of course)
so for chain+sprockets worn: -130
tires worn: -150
cables: -20 each
battery: -40
brake pads: -30
brake drum shoe: - 30
brake disc: - 60
fork seals leaking: - 30