MM: Have posted in other threads what you are mechuyav to give up to pay. Once again (as I learned there) this may not apply in Brooklyn, where tuition is not expected to be paid. The Psak I got was that it depends on what the school says (i.e. if they say “we will be happy with 60%” without any checking of income etc., then that is what they really expect).
I have no problem if you can pay what you need to by having your wife do “inside” work. The question is what to do when that is not possible.