Ex-player grands are usually worth about 1/2 of what their non-player counterparts might fetch.
If the player system is in good working order, they can be worth quite a bit of money in certain circles.
Rebuilders tend to stay away from the ex-players, as their action geometry is far from ideal.
Your question is not easily answered. How much is it worth to you? Or how much is it worth to the person looking to buy it from you? The two numbers could be quite different.