Hey Zaki,
This money is not going into economy as this is the savings from the salary that these Pakistanis send back home.
So like if i earn 80,000 $ a year, say in USA, i will send a part of that for my family, like mom and dad etc.
So when the money is wired to Pakistan or transferred, the local people will withdraw the cash in rupees, right? So that Makes the market flood with dollars (that i just sent) and rupees are then taken off the market. That way, the rupee strengthens.
If Pakistanis didn't send this money, then no one will buy rupee in the local market, and foreign currencies will continue to appreciate w.r.t rupee. Pakistani's cannot simply make this money. They have to earn it abroad and then send it.
It does help the local economy in a way, that eventually some of that 4 Billion $ will end up as our family members will spend the money on buying goods in Pakistan.