I was offered a non-working one with a decent cabinet/playfield, some bg flaking and missing 2 displays for $150. I've never had a system 7 before and didn't know if this would be worth the time and effort or not.
A far less popular game than it's brother, Firepower, and built in the time when manufacturers were feeling the video squeeze, so less features/imagination - including lack of speech.
$150 though is a good price, I can certainly help you with board needs if you have problems getting it going. Good luck with your decision.