I chose my unranked primary-care oriented state school over a top-20 school. Money was a major factor, but not the only one. I just couldn't be 100% certain that I would be happy at the expensive private school- and I felt the same way about the state school. So, I decided that it would be better to save the money and go to my state school. If you definitely like the top-5 or top-10 school better, go there. However, if you could be happy at your state school, save your money and go there. First, however, be sure to compare financial aid packages- some private schools offer enough financial aid to actually make them more affordable than many state schools. Unfortunately, the state raised our tuition a whopping 15% last year and another 15% this year- so I'm going to end up in almost as much debt as I would have had I chosen the other school!
Do I have any regrets? I'd be a liar if I said no. Overall, I have enjoyed my MS1 year- my school has a lot of great things about it and I've met some great people and had some awesome experiences. However, there are things about my school that annoy me and there are times that I find myself thinking "Gee, if I had chosen the other school, I wouldn't have to deal with this." Of course, every school has its weaknesses, so I'm sure I would have thought the same thing the other way. Overall, there are enough advantages to my state school that I'm still comfortable with my decision (in spite of the ridiculous tuition increase.)
Bottom line: go where you'll be happy- and don't let money be the only determinant of your decision.