If the $5m price the US put on Osama bin Laden’s head in 1998 had led to his immediate capture and disabled al-Qaeda, it would have been the bargain of the millennium.
Assuming that the September 11 2001 attacks would not have happened without bin Laden, and that the Afghanistan and Iraq wars would not have happened without September 11, the al-Qaeda leader directly cost American taxpayers more than $2,000bn – and the indirect burden may be much higher.
The contentious business of estimating the bill for September 11 has become a thriving cottage industry. The direct costs of the Afghan and Iraq operations are the easier part. The Congressional Research Service, Capitol Hill’s non-partisan think-tank, recently calculated that Congress had appropriated $1,283bn since 2001 on top of its usual military expenditure without adjusting for inflation and debt interest. The CRS estimates the costs will total $1,800bn by 2021.