I don't know. The most expensive game I know of is Pitfall II (back then) It cost $45 if I remember right, and it sold really well. But it was a huge awesome game for the time also. It cost a lot cause it was on a 16k cart, with a custom built 2k synthasizer chip to create it's beautiful music. It didn't have problems selling, but I dont know if people would have paid that much for Berzerk to talk.

Starpath Supercharger cost $50, but it was the promise of cheap games that sold it. You could buy the games for $%-$15 for it. Being on tapes made them cheap.