None of that really matters. The big ROI is just getting a degree or the type of degree. There are few elite schools that have a much better ROI but they tend to be very generous with financial aid anyway.
Also, community colleges are a great resource. As long as community colleges exist, we shouldn't even allow student loans for the freshman and junior year. You can do your first two years while working part time to pay the very minor tuition. Then you can transfer to another school. Every flagship state school takes tons of transfers. My buddy transferred from a podunk community college to Stanford.
And when you transfer you should go to a cheap school. Unless you get a great college scholarship, it should be your state's flaghship public school.
Nortwestern is a great school, but not 150k better than UIUC (and for engineering its not better period). If you get a nice financial aid award, great, but otherwise don't go. My college counselor in high school was telling people to pay full price for DePaul instead of UIUC just because they wanted a "city experience." No, that's not worth it.