According to a Congressional Research Service report, the
military operations since the Sept. 11, 2001 terrorist attacks have cost
over $1 trillion, making the “war on terrorism” second only to World
War II in cost to US taxpayers.
[legalift.wordpress.com] “CRS provided its estimates in current year dollars (i.e. the year
they were spent) and in constant year dollars (adjusted for inflation),
and as a percentage of gross domestic product,” noted Secrecy News
editor Steven Aftergood, who obtained the report. “Many caveats apply to
these figures, which are spelled out in the CRS report.”
Indeed, the author of the report, Stephen Daggett, wrote that
“Comparisons of war costs over a 230-year period are … inherently
problematic.”
Source: https://legalift.wordpress.com/2010/07/21/war-on-terrorisms-price-tag-1-trillion/