I can't speak to CA prices but in my area the gun stores I deal with would offer 70% of what they think they could sell it for. Based on that formula retail would be in the neighborhood of $575.00 used with 2 - 10 round mags instead of 13 rounders so trade in value would be about $402.50 (70%). Splitting the difference between estimated whole sale and retail one can arrive at a fair median private party sale value which in this case would be around $488.75. If it has night sights that still glow brightly then you could add $50 to $60 to the starting retail figure.
I would recommend looking at some of the online auction sites to verify my opinion. It's an experienced opinion but an opinion none the less. Good luck.