I am in the same boat. I also was accepted to Northwestern and would go there in a heartbeat if tuition wasn't so ridiculous. I've reached out to several SLPs who've attended other cheaper but still top-ranked schools (IU, Wisconsin-Madison, etc.) to hear what they have to say. One of them actually works at a hospital and her job is to hire recently graduated SLP students for their CF. She said that she would never hire someone just because they went to Northwestern over someone who went to another reputable program that's ranked a little lower. She also said that she knows several people who attended Northwestern and are now regretting it because they have such a ridiculous amount of debt to pay off. I've also heard people say that Northwestern has a bit colder/more intense of a feel than some other programs, and that it is very rigorous and much more fast-paced because of the quarter system. It's always good to take everything with a grain of salt though - I personally think Northwestern's program seems absolutely amazing! Talking to all these people in the field made me feel so much better about possibly choosing another cheaper program over Northwestern. I will likely decline my offer unless I were to by some chance receive a scholarship, and I feel like that's the best choice for me.
That being being said, paying off debt is of course possible and lots of people do it. If you are sure that going to Northwestern and getting to experience Chicago would definitely make you that much happier than attending another school, then maybe it's worth it for you! You just have to weigh how much that all matters to you I guess. I just don't think it's a good idea for people to go into that much debt just because they think they will automatically get a better job from attending a program with such a good name. From everyone I've talked to, that's simply not true. Remember that at the end of the day it's really what you make of it and you will be so successful regardless of which program you choose!
Regardless of where I go, I'm planning on babysitting on the weekends or finding some other part-time work on the side to off-set at least some of the costs. Also I second what was said above -- federal loans from the gov are a must!!