That’s three variables. You can also get a rather decent approximation, at least for private universities, with just two variables: (1) endowment, and (2) number of students.
Go to this [Wikipedia page](List of colleges and universities in the United States by endowment - Wikipedia). Scroll down to the table labelled “Endowment per Student”. Click on the column heading labelled “2015 Endowment per Student” to sort on that basis.
Top 20 Private Universities by this system:
Princeton
Yale
Harvard
Stanford
MIT
Caltech
Rice
Dartmouth
Notre Dame
Northwestern
Chicago
Duke
Penn
WUSTL
Emory
Brown
Vanderbilt
Columbia
Cornell
Rochester
This system, like any other, is imperfect. For example, it penalizes Johns Hopkins for its (relatively) small endowment. But that’s arguably unrealistic, because JHU is also (by far) the top university for [receiving R&D funding](Johns Hopkins leads U.S. in research spending for 36th year in a row | Hub), which compensates to some extent.