Meaning of sixty-four-dollar question

six'ty-four-dol'lar ques'tion

Pronunciation: (siks'tē-fôr"dol'ur, -fōr"-), [key]
  1. the critical or basic question or problem: Whether the measure will get through Congress this session or not is the sixty-four-dollar question.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.