Cheap, whatever. The big point is if you dump enough young workers into the system, you can push wages down almost arbitrarily.
At least until they drag you out of your house and stick your head on the end of a pike...
I would use the US H1B system as an example, 20 people living in a house (illegal but common), working for an employer that if they quit that job or want to work somewhere else, they're deported. You can fiddle around with the exact definition of slavery but it's disingenuous because they have the same impact as slaves did in ancient Rome.
