I saw a You Tube interview of Robert Duval, after Pt III, where he was asked why he wasn't in the movie. He said it was a money thing. (I also heard FFC say he was bankrupt at the time, and that is why he did Pt III.) Duvall said he refused to do Pt III because Pacino was getting five times more than he (Duval) was offered. He said he would have done it for two or maybe three times less, but not five.

Does anyone know how much Pacino was paid for GF3?