The Salkinds decided ahead of time to shoot “Superman” and “Superman II” back-to-back, which resulted in the assemblage of a 550-page script. Going by the minute-per-page rule, this would’ve been enough for four movies, so Donner brought Tom Mankiewicz on to pare down this draft.
Forced to complete two films at once, Donner worked out of sequence, shooting much of “Superman II” before completing everything he needed for the first movie. Given the pioneering visual F/X being developed for Superman’s flying sequences, Donner needed to know how much money was being spent at all times, if only to make informed decisions on where he should concentrate his efforts.
In a 2016 interview with The Hollywood Reporter, Donner revealed that the Salkinds stonewalled him every step of the way.
“They never ever told me what the budget was. I had no idea what I was spending. I was making a movie and they wouldn’t tell me the budget. So there was no way I knew what I was spending. Sometimes I’d authorize something and nothing would be there; they would just arbitrarily cancel it. They didn’t want anyone to know where that money went, I guess.”