So let me see: a person from another country receives a service that is exclusive, very limited and in high demand (PhD), pays for it, and that person eventually takes it back to country of origin.

US education must be in a woeful state because that is the definition of export.

Given the exclusivity and value of the service you'd think you'd want to hang on to it, but I guess xenophobia is one thing that is more important than money.

I've been hearing nothing but bad things about the actual education in US institutions. I think they've tarnished their name at this point to no return.

STEM PhD students do not pay for their education

STEM PhD students typically pay with labor rather than cash. Labor to teach undergrads, and to perform other university research. (though they typically pay their undergrad with large piles of cash).

That is, very much, a substantial form of payment.

This is manifestly not true. What leads you to believe this? Certainly there are some who don't, just as with undergraduate education. But there's no blanket program in the US to pay for all STEM PhDs.

All of the dozens of US STEM PhDs I know from recent decades had to pay their tuition by working as TAs, RAs, or usually both. They didn't walk in the door with a trust fund, work through the coursework, and then write up a dissertation. I'm not sure that's even a possibility in most STEM fields: you need access to millions of dollars of ultra-specialized equipment which you can realistically only get by working in an existing lab, which means being an RA.

Right, they work a job to pay for their tuition. But they still pay, even if it's bartered.

You have a point!

They work like a 120k a year job for 30k a year.

True, but I would say a large fraction of foreign nationals who do PhDs in the US were undergrad educated at least partially in the US.

Isn't that how exporting works? People buy something in one place and take it another?