You will need to take your math challenge to the Pentagon, not Steve Clemons. If you had read the article, you would have seen the ratio you referred to:

The Pentagon arrived at its much lower estimate by dividing its war funding request by the number of troops throughout the region: 68,000 in Afghanistan and up to 95,000 in supporting roles elsewhere, such as on nearby ships or in surrounding countries.

The Pentagon cost includes higher combat wages, extra aircraft hours and other operations and maintenance costs, but omits such items as new weapons purchases -- one-time costs that vary by year -- and support equipment like spy satellites and anti-roadside-bomb technology.
The Pentagon also does not try to estimate costs of new bases for additional soldiers.
But in a memo early this month, obtained by The Times' Washington bureau, the Pentagon's own comptroller produced an estimate that broke with the customary Defense formula and did include construction and equipment.
That memo said the yearly cost of a 40,000-troop increase would be $30 billion to $35 billion -- at least $750,000 a person. An increase of 20,000 would cost $20 billion to $25 billion annually, it said -- a per-soldier cost equal to or greater than the White House estimate.

Under questioning by the House Armed Services Committee this month, a Congressional Budget Office expert couldn't say how much it costs to run the wars in Iraq and Afghanistan.
"I find it astonishing that, eight years into this, we haven't nailed it down with precision," another witness at the table, David Berteau, director of the Defense Industrial Initiatives Group of the Center for Strategic and International Studies, said later.