Giving students from high income families a tuition discount likely won't change their decision to attend, hence price discrimination. To maximize charitable impact with respect to financial aid, it could be argued that instead the funding should go toward other schools so that these all-star, low-income undergrads have more opportunities closer to home.
[1] http://web.mit.edu/facts/tuition.html
[2] https://www.nytimes.com/interactive/projects/college-mobilit...