Endowments are not meritocratic. While I can't quote data, I imagine that wealthy students provide much more growth for endowments, which in turn contribute not only to reputation, but also research, and ratio boosting hiring capacity. While Princeton and other Ivies, do have aggressive financial aid programs, https://www.princeton.edu/news/2022/09/08/princeton-will-enh..., it is important for the elite schools to admit the wealthy, particularly students whose families will donate generously initially upon admission, and also throughout the student's life. Less wealthy students are less attractive fiscally, but reputation is influenced by a schools willingness to admit lower income students.