U.S. has spent $1,600,000,000,000 on war since 2001

"The cost of US war-making in the 13 years since the September 11 terrorist attacks reached a whopping $1.6 trillion in 2014, according to a recent report by the Congressional Research Service (CRS)." "A report by Neta Crawford, a political science professor at Boston University, estimated the total cost of the wars in Iraq and Afghanistan—as well as post-2001 assistance to Pakistan—to be roughly $4.4 trillion." (thanks Amir)