Here is a nice blueprint quote from a senior writer at CNBC. You can see the math breakdown a lot better.
Is college a good investment?
Calculate how much discretionary income a student would have after graduation, assuming he or she took out loans to fund an education at University of Massachusetts at Amherst, a public school, or private New York University. The calculation assumed the student earned a business degree, got a job making $65,900 (the median industry salary, according to the BLS) and paid 8 percent interest on the loans.
After factoring in everything from taxes to 401(k) contributions, Kotlikoff calculated the graduate paying off the debt from UMass would have $36,515 for discretionary spending. That would remain stable even after his debt was paid off.
The NYU graduate would never catch up. He or she would have $22,128 for discretionary spending at age 22, rising to $35,311 at age 42, when the debt is paid off.
Of course, there are factors that could make the higher debt more worthwhile. Perhaps the NYU graduate would find that degree translated into a higher salary over time, making the extra tuition pay off. But even at the most elite private universities, there are no such guarantees.