Hard to find an all metal gun for a price like that. I have the M15A4 rifle that I bought new just under 2 years ago. With a battery and shipping, it cost me just shy of $700. So yeah, it's a good deal if it's the CA Proline.
Now there's also the CA Sportsline which are their lower end models and now offer metal bodies. You can tell the difference by the trademarks. The Proline (high end) have laser etched trademarks, so they appear metallic (from the aluminum receiver). The Sportsline has engraved trademarks. If it's one of the Sportsline models, then you're still getting a fair price if the gun is in excellent condition. Usually the plastic Sportsline models sell in that price range new.
If that's what this gun is