$64,000 dollar question

The $64,000 Question was a popular United States television game show from 1955-1958; The $64,000 Challenge (1956-1958) was its popular spinoff show.
Such a question is now widely recognised as a standard phrase referring to the key issue, most important question. E.g.:-
--The $64,000 dollar question is will this camera be as sharp as the equivalent Olympus 35LE?:blush:

Το θέμα είναι αν αυτή η φωτογραφική είναι [...]

There is also the similar ερώτηση του ενός εκατομμυρίου.

"Το κρίσιμο ερώτημα", is the form I hear more often.