All exports/imports to and from Iran are in your favor.
Iran's government pays subsidy on many products including the gasoline, that's why they are much cheaper than the international market. so overall Pakistan pays less dollars for it and it helps your currency rate.
But it hurts Iran's economy, cause we are paying subsidy to Pakistan, we import gasoline from India, and sell it cheaper to Pakistan, so it has negative impact on our currency rate.
And what we import are the goods which are sanctioned, So pakistanis import it, then export it to Iran with higher price, no effect on your currency rate, but it creates job for Pakistanis, so again it's good for your economy.
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Through those so called proxies we have ruined our enemies' plans, if it wasn't for them, now we had to deal with isis terrorists inside Iran.
if we wouldn't help Hamas, Israel wouldn't need to expend billions of dollars to develop it's Iron dome, so they would have had more money to fund anti-Iranian terrorists inside Pakistan.
They are part of Iran's deterrence policy, those walls aren't.