The Money Quote

Well no less then William Safire, the noted etymologist, explains the term 'the money quote' and ties it right into the term 'the money shot.

http://www.iht.com/articles/2005/03/13/features/saf14.php

A money quote has subsumed blurb's primary meaning of "recommendation that helps its object make money," adding the sense of "the essence, or most newsworthy part of the statement."
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In horse racing, the money position was the front. In baseball, The New York Daily News wrote in 1949, "Pee Wee Reese … Duke Snider … and Luis Olmo … came through with money hits to break the tie." (And where was Carl Furillo?)

Then money as a modifier meaning "powerful, decisive" made the move to movies as money shot. Steve Ziplow, in his "Filmmaker's Guide to Pornography," noted in 1977 that "there are those who believe that the … money shot is the most important element in the movie." The staid but resolutely unblushing Oxford English Dictionary, now available online for $295 a year, cites this climactic phrase as an American colloquialism for "a provocative, sensational or memorable sequence in a film, on which the film's commercial performance is perceived to depend; (specifically, in a pornographic film) one showing ejaculation); … (also, in extended use) a crucial or pivotal moment, event or factor, especially in another art form, as a novel."

Now, how can that tie into 'show me the money'?