You have to take into consideration of the living expenses as well (that's the first thing that came to mind). However, as I'm typing this, I kind of realize that what I just typed is probably wrong.
Yup, because this is the amount for tuition only. Then again, HBS has a mandatory 4800 fee for books, cases etc. Columbia and Wharton have books and supplies fees but only about 2000- 3000. Still that doesnt make up the difference.