The Pentagon is inflating its expected costs for the advisory mission in Afghanistan next year, according to a defense expert.
Todd Harrison, senior fellow at the Center for Budgetary and Strategic Assessments, says that as the number of troops deployed drops, the costs for the Afghan mission should be falling at a similar rate.
That is a significant uptick from the $2.1 million cost per troop in 2014, and from the average cost of $1.2 million per troop between 2005 to 2014.
The $42 billion is eight times more than the $5.3 billion that's expected to be requested for the war against the Islamic State in Iraq and Syria.
Harrison said the high costs were more likely due to the Pentagon and Congress wanting to stuff more money in the Overseas Contingency Operations budget to pay for things that would normally come out of the base defense budget.
"It is being used to supplement the base budget. They are classifying things that used to be in the base budget, and we are saying that it is for Afghanistan now," he charged.
Pentagon officials, though, argue there are extra costs to the drawdown from Afghanistan.
Harrison said the argument doesn't make sense since it did not cost as much to build and send the equipment over during the mid-2000s at the height of the war.
"It doesn't explain it, it's not even close. Yes, there is a cost of shipping things back, but it doesn't explain what we're seeing here. It's a red herring," he said.
OCO funding is not subject to budget caps mandated under the 2011 Budget Control Act, which essentially cut $1 trillion from the federal budget, and roughly $500 billion from the Pentagon, over a decade.
"The incentive there is to reclassify anything you can as being OCO funding, and both DOD and Congress have been doing that," Harrison said. "And it is hard to track specific things."
Budget hawks have long accused the Pentagon and Congress of using the OCO account, also known as the Pentagon's war fighting budget, as a "slush fund" as the overall defense budget becomes more constrained.
Harrison said Congress was responsible for shifting $10 billion from base funding to OCO funding in 2014, and about half of that in 2015.
This story was updated at 4:36 p.m.