We have been through this revenue bull$hit several times here. Revenue is being collected in Karachi not generated. That revenue that you “collect” at Karachi port in terms of custom duty and sales tax, is eventually paid for by the buyers all over Pakistan mainly from teh bara suba.
Bara suba also contributes 70% of Pakistans exports in terms of rice, leather and leather goods, sports items, surgical instruments and cutlery.