Ive seen multiple ICB sell unworking/unrestored for $600-ish in the last few months.
550-600 for a working one is a great deal.
I bought 3 a little while ago and have been working on them.
Problems I have encountered (thanks to all who helped me so far, especially pcjohn):
The bases are all totally destroyed. Need to buy new ones (I ordered 3 from spacebaby)
The power chassis all have at least 1 bad bridge rectifier.
The belts are all broken. I bought some from marcospecialties.com, but the Bob Roberts method should work as well.
The vertical bars and horizontal rod are gummed up bad with old grease, cockroach legs, etc.
There are many switches in the game. Some needed adjusting (use test mode).
-->I found some were actually miswired.
Someone tried to wire up a "free play" button, and wired it wrong (NC instead of NO), causing the game to not keep score.
The bezels all have some amount of cracking/peeling. I believe these are due to be repro-ed by Phoenix Arcade.
The CPOs are all cracked at the right angle turn in the front. These repros are available now.
Don't overlook the balls. Mine were nasty and had tiny pits/chips. New ones from marcospecialties.com are cheap.
The playfield has grease/oil trails from where the ball comes out. Be careful cleaning that.
The back doors were in fair to poor condition. I replaced them.
The 4 limit switches need to be adjusted to be "just right"
Typical stuff with the cabinet (wood chips, peeling vinyl, side art, etc)
There was a HUGE spider making its web inside one of the power chassis, which viciously jumped out at me and caused me to hit my head on the cab. It hurt.
One game is blowing a fuse, haven't figured out why yet. I know it isn't the power chassis, playfield, or board (swapped in known good parts from other machines). Must be coin door, control panel, or wiring harness I guess. Probably another radioactive spider waiting for me in one or more of those places.