It is against rule for under 100 post to sell on here but I would say it can be worth about 500 dollar. If it is touch screen, that would be 600 to 700 dollar.
I don't think he's trying to sell it here so he's not breaking any rules. I know jack about laptops but if you're selling it on Craiglist pick a price your comfortable with then add an extra 30ish percent or so and start that as your asking price.
I'd say ask 550 to start and see what you can get for it.