In Average shape they seem to sell for around 800...that's with a nice backglass. I paid double that for a fully mylar'd one with no PF wear to speak of. You wont get a lot of chances at finding a nice one so don't hesitate to pull the trigger if one comes along. The game doesn't get much respect but I think its great.

I bought one with a nice playfield, backglass bad with the 3-D eye insert for $200 with repairable boards and a pretty faded cabinet. I was able to clean it up and I had a NOS backglass from a warehouse find. I love the game and I think anywhere 900-1400 for one in nice shape is reasonable. Especially unfaded.

the norm is 500 to 600 working unless outstanding shape with new boards, etc.
a very nice one was sold on cl in michigan for $500 or lower recently. prob the nicest one out their physically.

I don't see to many Bally games from the early 80s show up for sale, so it's really hard to get a grasp on the pricing. I picked up a non-working one recently, and hope to get a few months play out of it once fixed before selling.

It takes 250 dollars just to get a game working right so I don't think 500-600 is reasonable for a nice working game. Something north of 750 but a mystic is hard to find in any shape. I love the game.