If this is true (I doubt it happens at scale), then the US got to benefit from some severely underpaid labor for a couple years at no cost to the taxpayer. What's there not to like?

It happens at scale. UK universities are also heavily subsidised by Chinese students. I also, where I am, I don't really see these students working in part-time jobs to pay the bills.

I assume the underpaid labor they were talking about was the PhD.

PhDs get paid though?