The NYT has an interactive infographic that attempts to break down the financial cost of 9/11.

Graphic:
http://www.nytimes.com/interactive/2011/09/08/us/sept-11-reckoning/cost-graphic.html

Article:
http://www.nytimes.com/2011/09/08/us/sept-11-reckoning/cost.html


First three paragraphs of the article:

<< In 2004, when he was arguably still capable of initiating another devastating attack on the United States, Osama bin Laden released a video gloating about his plan of "bleeding America to the point of bankruptcy."

<< As usual, Bin Laden's vow was overblown -- but, as it turned out, not entirely crazed. A survey by The New York Times, detailed in the accompanying chart, puts a stark price tag on the cost of reacting -- and overreacting -- to the defining event of the past decade. America's bill for fighting a 21st-century "asymmetric war" comes to at least $3.3 trillion. Put another way, for every dollar Al Qaeda spent to pull off the Sept. 11 attacks, the cost to the United States was an astonishing $6.6 million.

<< Today, Al Qaeda in Pakistan is crippled and Bin Laden is dead. But the $3.3 trillion figure suggests that the unanticipated costs of how we managed a grim decade -- money already spent or committed in the future -- amount to a little more than one-fifth of America's current national debt. >>

(Unrelated: That's five dashes in three short paragraphs.)