> I really don’t think it’s much harder to prove that an underperforming student who got in because their parents donated a couple million (or tens of millions of) dollars took the place of a more qualified candidate.

It's the opposite actually; if you're giving money to the development office then you're enabling more qualified students to attend the school.

That’s why college only costs 50k per year when it costs 150k to provide that service to you.