Money

William Eggleston, Untitled (Memphis), 1970
This photograph recently sold for $245,000.
Helen Levitt, New York, 1980
But you can get this one for $12,000.
What could account for that disparity? Simple. Marketing. And the fact that the venal clowns who run the real world also run the art world. Consider, for example, this statement by Tobias Meyer, head of contemporary art at Sotheby's:
"The best art is the most expensive art because the market is so smart."
See? A real neocon. Next, Sotheby's will feel compelled to declare war on Iran. (Or would, if there were any antiquities left to loot.)
(For an interesting discussion of the marketing of these pictures, read Amanda Doenitz's article in the current Art on Paper. And check out Sotheby's new MasterCard, through which you can get, among other must-haves, "a helicopter tour of the California wine country with a Sotheby's wine specialist." Hmm. Pretty cool. And such an efficient use of your valuable time.)