The original US early 1960s quiz show amount, and therefore the correct expression used, was the $64 (and not 64,000) question. Time and people's tendency to inflate everything took care of the rest.
Where did you get that idea outdoor man? No-one would watch a game show called the $64 question.
It's a real show, they actually gave away $64,000. It was presented by a guy called Hal March in the 50s and was on one of the major networks.
I think that the original game show was the $64 question (a radio show in the 1950s, I think) but it was revived/reinvented in later decades as the $64,000 question (due to increased commercialisation as well as inflation). The same idea has now evolved to become Millionaire.