I think that Jai's giving of a blank cheque to Bani has some special significance. I do not feel that he is so insensitive as to not buy a gift for her...
Perhaps in his helplessness he is symbolically giving everything he owns to Bani..and himself to Pia!
Isn't that what she wants?
After all she 'loves' Mr. Walia.
Will she still do if he is penniless? I think Jai knows the answer to this and that is the only way open for him to escape Pia's and Jig's tentacles!