$600 is far too little, but I also believe that $1500 will not sell (you're still more than welcome to try).
Partially because this model is newer and better:
MSI G Series GT600NC-004US ($1500)http://www.newegg.com/Product/Product.aspx?Item=N82E16834152337
The price is automatically lower because your laptop is used and the parts are from the last generation of hardware.
For your laptop a reasonable list price is $1200, but a cheapskate wouldn't spend more than $1000.