I posted on this a while back. I copied and pasted what I wrote before below:
So I spoke to a financial aid officer there, and here is the example he gave me of how debt cap works:
Assume that after you turn in your financial paperwork, it is assessed that you should contribute 10,000 per year. However, your budget for the year is 60,000. Therefore, you will have to take 50,000 in need-based loans. After 4 years, you will have accumulated 200,000 in need-based loans. Therefore, NU will knock off the extra 65,000 so that you only owe 135k (the class average).
But the above scenario assumes you were only expected to contribute 10,000. If you are more well off, you could be expected to contribute 20, 30 or even 40 thousand, which qualifies you for a much smaller need-based loan, although you can still get normal loans if you really can't pay the contribution they expect.
So lets assume you have to contribute 30,000 per year. Then, you would qualify for a need-based loan of around 30,000 each year x 4 years, which is 120,000. Therefore, you would not benefit from the debt-cap at all.
If they ask you to contribute 30,000 and you end up taking out loans for the entire amount (60,000 each year, or 30k in need-based loans and 30k in regular loans), you end up with 200k + in loans, but the debt cap doesn't help you since your need-based loans are still under 135k even if your total loans exceeds this amount.
In conclusion, they will only knock off need-based loans that exceed the class average, but not normal loans, and the amount of need-based loans you will be granted depends on how much they expect you to contribute out of your own pocket. So if you are expected to contribute a lot, you won't benefit from the debt-cap.
I guess my conclusion is: NU will expect most people to contribute a significant amount, qualifying them for little need-based loans and making it unlikely that they will be able to use the debt cap. Of course, some people will benefit, but I am guessing the majority will be at or below the debt cap.