In STEM, federal grants pay for almost all US PhD students. And the tuition they would charge would never have covered the actual cost. It has always depended on research grants. Which makes sense, a PhD is mostly and apprenticeship in how to do cutting edge research.

The article mentions that a major factor in technical grad school is research funding. Most grad students in engineering, for example, don't pay tuition themselves. They work for a pittance and receive tuition as a benefit.

Yes, and it's even spelled out explicitly earlier in the letter.

> For departments across the Institute, the funding uncertainty I talked about has made them cautious about admitting new graduate students.

Yes of course they could admit any person who didn't finish high school.