i paid 200$ for mine way back in 2010, and she's in really good condition. i know thats probably not much help, but i would expect her to easily sell for over 300$ now, she doesn't come up that often and i absolutely jumped on it when i saw her. 600$ seems a little high to me, but then it all depends who's looking and how much they're willing to pay.
do correct me if i'm wrong, anyone...?