Why didn't you take the offer?
Students do not have to pay tuition if their parents make less than $140K a year. Students receive a full-ride (including tuition, room & board, and a stipend for misc costs) if their parents make less than $65K
Sources:
http://money.cnn.com/2015/04/01/pf/college/stanford-financia...
https://www.princeton.edu/admission-aid/affordable-all
Personal anecdote: I recently graduated with zero debt from Princeton (in fact, with a net positive gain in capital) and I come from a upper middle class family.