I'd bet it's your knee-jerk counter-spin that's fail, but there's not enough detail to tell for sure. Generally when talking about shared costs it is customary to allocate them proportionately across all of the "consumers." For example, if 20% of the fuel goes to run air conditioners, then 20% of the cost of fuel convoys is allocated to the "Air Conditioning Expense" bucket.
I'm guessing that's what the general did here (but again, that's an assumption). In any case, it doesn't seem like an unreasonable expense. I have no doubt it's damned expensive to air condition tents, and I fully support offering such comforts to troops whenever we reasonably can. It's really a drop in the bucket compared to the total cost of the wars, and simply underscores that immense cost. It's just another reason why we should get out as fast as is safely possible.