thats the $64,000 question

Thats the $64,000 question is a cliche due to the same dollar amount being used in most cases of when this phrase is spoken. What this idiom means is that it is a question that is the most important and most difficult question to answer concerning a particular problem or situation. It is usually spoken to the person who seems to pinpoint the most difficult question to answer in whatever situation or problem it is pertaining to.