What type of consequences? If a family thinks in September that they can be full pay at NYU but in April decide that they aren’t really comfortable taking the risk, they can pull their application. NYU won’t send them a bill. Your kid’s high school might hold it against you and refuse to send final transcripts to any but your state schools. I don’t think they can legally do that but I think some do.
I think $70,000/year is a lot to spend. It’s easy to think that everything will go right – the family finances won’t be affected by death, divorce, or disability, or the student won’t have medical or academic issues and have to withdraw – but these things happen. If families decide they aren’t comfortable paying they should reject the ED offer. It’s easy to say don’t do ED if you’re not sure you can pay, but I don’t think it’s unusual for people to think/hope they can make it work and realize later they really can’t without risking their retirement. Only you know what’s right for your family. I wouldn’t submit an ED app to a school unless I had some idea I could pay, but if I did and changed my mind about it’s affordability I wouldn’t hesitate to reject the offer.