They way you see what a laptop is worth is to pull up comparable laptops.
Goto EBAY. Google your laptop. See what a seller with good rep is getting. Then drop your price another $50 unless you have a good rep with 100s of positive feedback. Alternative find a friend who needs a lappy and cut them a good deal.
I personally would not buy a used laptop from someone I didn't know, laptops lead a hard life and (unlike desktops) the parts that fail (MB, Screen) are expensive and are a pain to swap. This type of thinking cuts the resale price of used laptops.