Treasure of the Sierra Madre1948

Howard:
Say, answer me this one, will you? Why is gold worth some twenty bucks an ounce?

Flophouse Bum:
I don't know. Because it's scarce.

Howard:
A thousand men, say, go looking for gold. After six months, one of them's lucky. One out of a thousand. His find represents not only his own labor, but that of nine hundred ninety-nine others to boot. That's six thousand months, five hundred years, scrambling over a mountain, going hungry and thirsty. An ounce of gold is worth what it is, mister, because of the human labor that went into the finding and getting of it.

Flophouse Bum:
I never thought of it just like that.

Howard:
Well, there's no other explanation, mister. Gold itself ain't good for nothing except making jewelry with and gold teeth.