The $9B figure is total amortized to yearly: research, development, production, and maintenance across the near century of lifetime (1990s-2080s).

I took the total number of graduate students, to spread the money across them. We could also look at the same number as, eg, funding an increase from 3.1M to 3.3M or 3.4M graduate students.

I stand by my original claim:

A 10% increase in graduate salary or number of students doesn’t justify dismantling our air force.

$9B/yr is less than half of the Pentagon's more recent estimate of $2T through 2088 for the F-35 program (according to Wikipedia and its sources, which is all I have to go on).

And again, the F-35 is not synonymous with the entire air force.