The total cost to the United States of its wars in Iraq and Afghanistan, plus the related military operations in Pakistan, is set to exceed US$4 trillion ($4.8 trillion) - more than three times the sum so far authorised by Congress in the decade since the September 11 attacks.
The staggering sum emerges from a study by academics at the Ivy League Brown University that reveals the US$1.3 trillion officially appropriated on Capitol Hill is the tip of a spending iceberg.
If other Pentagon outlays, interest payments on money borrowed to finance the wars, and the US$400 billion estimated to have been spent on the domestic "war on terror" are added in, the total cost is already somewhere between US$2.3 trillion and US$2.7 trillion.
And even though the wars are now winding down, add in future military spending (and above all the cost of looking after veterans, disabled and otherwise) and the total bill will be somewhere between US$3.7 trillion and US$4.4 trillion.
The report by Brown's Watson Institute for International Studies is not the first time such astronomical figures have been cited; a 2008 study co-authored by Harvard economist Linda Bilmes and Joseph Stiglitz, a former Nobel economics laureate, reckoned the wars would end up costing over US$3 trillion.
The difference is that the financial position of the US has worsened considerably in the meantime, with a brutal recession and a federal budget deficit running at some US$1.5 trillion annually, while healthcare and social security spending is set to soar as the population ages and the baby boomer generation enters retirement.
Unlike most of America's previous conflicts, moreover, Iraq and Afghanistan have been financed almost entirely by borrowed money that sooner or later must be repaid.
The human misery is commensurate with the figures.
The report concludes that in all, between 225,000 and 258,000 people have died as a result of the wars.
Of that total, US soldiers killed on the battlefield represent a small fraction, about 6100. The civilian death toll in Iraq is put at 125,000 (rather less than some other estimates) and up to 14,000 in Afghanistan. For Pakistan, no reliable calculation can be made.
Even these figures only scratch the surface of the suffering in terms of people injured and maimed, or those who have died from malnutrition or lack of treatment.
"When the fighting stops, the indirect dying continues," said Neta Crawford, a co-director of the Brown study. Not least, the wars may have created around 7.8 million refugees.
What the US achieved by such outlays is also more than questionable.
Two brutal regimes, the Taleban and Saddam Hussein, were toppled while the al-Qaeda terrorist group that executed the 9/11 attacks has by all accounts been largely destroyed.
But in neither Iraq nor Afghanistan is democracy exactly flourishing, while the biggest winner from the Iraq war has been America's arch-foe Iran.
Osama bin Laden and his henchmen probably spent the pittance of just US$500,000 on organising the September 2001 attacks, which killed 3000 people and directly cost the US economy US$50 billion to US$100 billion.
In 2003, President George W. Bush proclaimed that the Iraq war would cost US$50 billion to US$60 billion. Governments that go to war invariably underestimate the cost - but rarely on such an epic scale.
If the Brown study is correct, the wars that flowed from 9/11 will not only have been the longest in US history. At US$4 trillion and counting, their combined cost is approaching that of World War II, put at US$4.1 trillion in today's prices by the Congressional Budget Office.
Death toll estimates (2001-2011)
* Iraq: 151,471
* Pakistan: 39,127
* Afghanistan: 33,877
* Total: 224,475
Figures include US military, US contractors, allied troops, Iraqi, Afghan and Pakistani troops, civilians, insurgents, media, aid workers.
COUNTING THE COST
* 2001-2011: US$1.3 trillion
* 2012: US$130 billion
* 2013-2015: US$168 billion
* 2016-2020: US$155 billion
* Total: US$3.7 trillion to US$4.4 trillion
Source: Brown University, Independent