Can grab a 48-1 for $100, so mid-$600's might be ok if monitor/chassis is in good shape.  These 4 player Gottlieb Challengers are the best cabs around in my opinion.

I passed up one in Sydney a few months back for $400 with a 26" Nanao dual res in it and a couple of working PCB's.  Couln't justify it at the time   If only.......