Because I can't quite see how it's an actual factor? If we're talking deans and university presidents, the numbers are just too low to make a difference for universities with tens of thousands of students. Plus, obviously, some Dean of Harvard Law might be earning millions but would still be underpaid relative to what they could command in the private sector.
If it's "administrators" as in "lowly" bureaucrats, how do they have the power to be given salaries beyond what's needed to attract them in the marketplace? If we compare their relative level of education with your average San Francisco Javascript coder, are their salaries still too high?
Speaking of COBOL: University IT staff, which would seem to be among the categories of "administration", is almost stereotypically underpaid compared to the private sector. Staying within the PhD comics universe, graduate students, postdocs, and other non-tenured faculty often have to fudge the numbers to delude themselves into believing they make more than minimum wage. This would also seem to disprove any theory that universities are particularly generous or incompetent when it comes to labor exploitation.
Beyond that, it seems strange how you are linking these two issues, of administrative salaries and foreign students. There is absolutely no reason to believe that money coming in via these students is different in any way to, say, grants or patent royalties or donations from alumni or really any source of income.
Foreign students pay more than their relative share of costs. Thus, they lower costs for everyone else. They take nobody's spot, but allow for more (subsidised) US students to attend.
This holds as long as an additional $1,000 made from foreign students does not, on average, result in admin salaries rising >$1,000. That would seem to be a pretty safe assumption, and I doubt anyone can come up with a plausible mechanism for why it should not be the case.
It really seems to me like you have two rather specific grievances, the choice of which I can't really explain except that I have a tingling sense they might have distant roots within the same corner of the ideological spectrum. And because these are your associations when the topic of universities comes up, or because you believe it helps to validate each, you've drawn some connection between the two.
But since neither is particularly well-tethered in reality, they really don't have much support to offer each other.