The Somalians are only "cheap labor" if the value of their productivity is much better than the cost of their pay. Stoned folks are not that productive. And have to be paid at least minimum wage
Considering the fact that extreme violence seems to be the hallmark of khat users, I suspect this new cheap labor is going to cost a great deal.
On paper, I would imagine a Somalian warm body looks like a Mexican warm body. On the factory floor it may be quite different - or it may not.
I stand by my economic hypothesis. Revenge would be throwing good money after bad.
Sounds like this stuff is a low-grade speed. That might cause an increase in productivity, unlike other substances which would probably slow most employees down.