How do professors spend their NSF grants? If a professor receives $200,000 as the PI (not co-PI) from the NSF, how many PhD students can he/she take as Research Assistant (with yearly salary of $18,000)? I am asking about the most usual cases. How much money does he/she need to handover to the department? How does this budget usually work? Does the professor also need to pay the tuition of the funded PhD students? Or does the department pay it? Very interested to know.
Ficticious but reasonably realistic example; YMMV, sometimes significantly:

Fall/Spring:


Stipend: $9,000/semester
Tuition: $7,000/semester @ 50% off
Health insurance: $1,000/semester
F&amp;A overhead: $5,400/semester @ 60%


Summer:


Stipend: $9,000
Tuition: $0
Health insurance: $1,000
F&amp;A overhead: $5,400 @ 60%


Total: $60,200 per student*year. In the example above F&amp;A overhead is 60% of stipend only, with no overhead on tuition or health insurance. Tuition is 50% off because it's an overhead-bearing grant.

So your $200,000 would be 1 student over 3 years plus some leftover for PI Summer salary, travel, misc. expenses, etc.