Builder — Builder asking money for noc

Address: Mumbai City, Maharashtra, 400079

I am urgently looking to sell my flat and builder is not ready to give noc without paying in cash. There seems to be no recourse. The builder is well connected, while we have no such connections and need to urgently complete the transaction. What do we do? Why is the builder noc required by banks who lend money. This is totally unfair for the seller as well as buyer as both have to bear the brunt.