Tom:

The "$4 billion a month for ten years" number is raw horseshit, although as with any useful lie, I expect to see it for the next year in every damn argument from the Left.

A "useful lie"? Tom, that figure came from the Pentagon!
CBO:

According to the Department of Defense (DoD), the occupation is costing about $3.9 billion a month to sustain.

Well, Tom, if that's a lie, excuuuuuuse me for being fooled by the Bush Administration! (Hell, you'd think I'd be used to it by now.)

My numbers are based on the statements of officials like Bremer, and I'm including all of the estimated costs of occupying Iraq indefinitely, including reconstruction and infrastructure improvement. The CBO analysis is very narrow and covers only the incremental cost of direct military operations (more on that bit of smoke-and-mirrors later). Nevertheless, I'll humor you by going through it point-by-point.

The CBO was only analyzing the cost of the military forces stationed there, from the standpoint of what we could afford and not necessarily what those in charge think we need:
CBO:

In performing its analysis, CBO made no assumptions about how long the occu-pation might last or about the size of the force that might be necessary. Instead, CBO’s work focused on determining how large an occupation the U.S. military could sustain in Iraq indefinitely—while still maintaining acceptable levels of military readiness and not jeopardizing the quality of the all-volunteer force—under various policy options.

In other words, this is a budgetary exercize, not a policy paper. The reality is that Bremer's been asking for more force than the 150,000 troops he already has. The CBO didn't even try to estimate the cost of that, because it concluded we couldn't afford more than about 106,000 past March of next year anyway. That's the $19 billion price tag.

The handwaving doesn't stop there:
CBO:

The estimates included in this analysis represent the incremental costs that DoD could incur above the budgeted costs of routine operations. As a result, those esti-mates exclude items such as basic pay for active-duty military personnel

"Incremental costs" only. Do you think we shouldn't include the base pay of the soldiers in Iraq in the cost!??! Maybe you're too used to the smoke-and-mirrors of the military-aerospace complex, but in real life no business could legitimately exclude those costs. This thing reads like an Enron financial statement.

The picture gets grimmer as you read on. About halfway through, it starts to talk about desperation moves to scrape up more troops beyond 106,000. Among the things it suggests is scrapping rapid reaction forces to free up another 10,000 or so, but at a cost:
CBO:

If the requirement for Army rapid-reaction forces was eliminated, DoD would have less ability to respond to new contingencies. The Army would no longer have available a reserved pool of units at the highest levels of training and readi-ness; in addition, the number of combat brigades available for other missions would decline by between 2a and 2b. If a contingency required a rapid response, DoD could use other Army units, but they would probably be less well prepared for immediate deployment

Another 8-11,000 troops could be raised by calling up the National Guard. They even consider using Special Forces and the Marines for occupation duty, with the same negative impact on military readiness outlined above (almost as if the same paragraph was copied and pasted). See Appendix C for a discussion of the negative impact on readiness.

This is why it's not legitimate to account for only incremental costs. The base costs are tied up in Iraq too, since those forces could not easily be shifted elsewhere in an emergency. The shortfall would have to be made up by expanding the size of the military or calling up more reserves--if we have to spend new dollars on new troops, or incur new expenses to call up the reserves, then the base dollars pinned down in Iraq should be charged to the Iraq account.

Ya know, Tom, you're still not seeing the forest for the trees. Suppose the CBO's right, and we ignore the hidden costs and the cost of reconstruction, and turn a blind eye to the deleterious effects on military readiness. Suppose the cost is "only" about $24B a year instead of $48B. That only cuts the cost in half..."only" 7,000 to 10,000 times as expensive as purchasing Alaska and the Louisiana territories. How is it suddenly a bargain if you use the CBO's numbers?

This has been an interesting exercize, Tom. Between uncovering costs that were swept under the rug, and showing how the Iraq occupation is undermining national security in terms of readiness, you've just shown how Iraq is a worse deal than I thought.