BLOOD AND TREASURE…. There’s no shortage of questions about how best to proceed in Afghanistan. By now, most of them are entirely familiar: would an escalation improve security? Can the Karzai government be relied upon? Is there an exit strategy? How many more U.S. casualties are we prepared to tolerate?

But there’s another element to the debate that’s generally overlooked, but which may come into play: can we really afford to keep the longest conflict in American history going?

While President Obama’s decision about sending more troops to Afghanistan is primarily a military one, it also has substantial budget implications that are adding pressure to limit the commitment, senior administration officials say.

The latest internal government estimates place the cost of adding 40,000 American troops and sharply expanding the Afghan security forces, as favored by Gen. Stanley A. McChrystal, the top American and allied commander in Afghanistan, at $40 billion to $54 billion a year, the officials said.

Even if fewer troops are sent, or their mission is modified, the rough formula used by the White House, of about $1 million per soldier a year, appears almost constant.

Budget estimates suggest we’re poised to begin seeing tens of billions of dollars in savings as a result of withdrawal from Iraq. Escalating the conflict in Afghanistan would, of course, eat up those savings and then some.

There tends to be an unspoken rule in our political discourse: the most aggressive voices on cutting spending, lowering the deficit, and trying to get the budget under control are the same voices who believe spending on defense, national security, and wars don’t count. Indeed, a wide variety of conservative Republicans complained bitterly earlier this year when the Obama administration raised defense spending, but not as much as the GOP hoped (they labeled the increase a “cut”).

The problem, of course, is that Pentagon spending is a huge portion of the federal budget, and wars are extremely expensive. For those policymakers intent on cutting spending, this would seem like an obvious area for savings — except they’re arguing the exact opposite, and no one presses them on how they propose we pay for it.

The NYT added, “Others said some Republicans could find it hard to justify a yes vote on troops after criticizing Mr. Obama for his spending.”

I doubt it will be too difficult — consistency isn’t their strong point.

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Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.