BCCI is one of the richest cricket borad which can even influence ICC but which is not the case of PCB, they cannot afford huge expenses to organize their their league with such super star players but PSL is also getting good record views for various reasons so its good for the cricket enthusiasts in that country.
Pakistan do have a cricket crazy population of more than 200 million, and more importantly there are large expat communities in the UK, US and the middle east. But then, the franchise T20 calendar is already saturated. Almost all of the test nations (perhaps with the exception of New Zealand) have come up with such leagues. Obviously this will mean less viewership, and thereby less revenue for each of them.