You can walk away from ED if the financial aid package is not adequate, too. And in this case the student determines what is adequate and what isn’t. The only “penalty” is that you have to relinquish your acceptance to Chicago. and you can’t wait to see what other colleges offer you before making that decision.
It would be crazy to enroll anywhere assuming that, without your parents’ credit, you were going to earn, borrow, or get scholarships amounting to $27,000 per year. That’s completely unrealistic unless you already have a small business that you don’t need to spend more than 15-20 hours/week running that generates that kind of cash flow.