They have to pay their thugs. Now that Iranian citizens are starting to come out at night and knife them, a particular cost/benefit ration emerges amongst the Basij:

-Go to work, maybe get knifed?
-Or stay at home since the pay is getting thin?

Decisions, decisions.

Oh, that's any easy problem to solve. You tell your thugs that if they stay home, the elite thugs will go to their house and execute them. No "maybe" there. So the thugs are better off showing up to work. And there's always money to pay the elite thugs, even in the most bankrupt and impovershed countries.

That's the whole beauty (dark irony there) of an authoritarian dictatorship. You don't need to rely on the willing cooperation of people, so you don't need to provide for their well-being or success or even pay them much at all. The higher up folks - which includes all your elite secret police and domestic security enforcers - are always complicit in the crimes of the regime, so they know they're up against the wall if the regime falls.