Amitabh Bachchan did Chehre for free, but why this generosity?

Amitabh Bachchan loved the script of Chehre so much that he agreed to do the film in no time. He was so generous that he did not charge a single penny for the film and also paid his traveling expenses. This was not the first time when Amit Ji was so generous towards his co-workers, He did not charge a single dime for The great gatsby. Ajooba, which was directed by Shashi Kapoor was a huge disaster. Amit Ji refunded 50% of his fees after the flop. This made me realize that how respectful Amit Ji is towards his co-workers. I doubt if there will be more like him or not.