Depends on the condition. I bought one a few months back in very good condition for $600. If it needs work I wouldn't pay over $300. Original parts can be expensive and hard to source for these suckers.
+1
If he's selling other games then he's a friggin liar and is most likely selling you a cabinet with a busted tube. I said busted tube not unworking monitor. You're buying metal for $75.00. If you have another monitor laying around doing nothing then this would be an awesome deal.
I've seen the same cab listed before on craigslist from that seller. Robotron Jon's right, he had it listed before for 700 bucks with a mulitgame board in it. $75 bucks isn't bad, but finding a monitor for that cab won't be easy, it's a 26" monitor.