NY Times reported only CBO's low-end estimates for troop increase cost, manpower needs
In a report released February 1, the Congressional Budget Office (CBO) estimated that President Bush's plan to send 21,500 additional combat forces to Iraq would also require sending 15,000 to 28,000 support troops. The CBO put the cost of the total increase between $9 billion and $13 billion over four months, and between $20 billion and $27 billion over the course of a year. But in a February 2 article  on a Senate Armed Services Committee hearing on the nomination of Gen. George W. Casey Jr., the outgoing top U.S. commander in Iraq, to be Army chief of staff, The New York Times informed readers of only the low end of each of CBO's estimates.
From the CBO report  on the estimated costs of increasing U.S. forces in Iraq:
The President has announced an increase in Army and Marine Corps forces to be deployed to the Iraq theater of operations. Over the next several months, that increase will be accomplished largely by deploying troops sooner than was previously planned and by lengthening the deployment of forces already in the Iraq theater. The increase in force levels has already begun and is expected to reach its peak of about 20,000 additional combat personnel in May.
Over the past few years , DoD's practice has been to deploy a total of about 9,500 personnel per combat brigade to the Iraq theater, including about 4,000 combat troops and about 5,500 supporting troops.
To reflect some of the uncertainty about the number of support troops, CBO developed its estimates on the basis of two alternative assumptions. In one scenario, CBO assumed that additional support troops would be deployed in the same proportion to combat troops that currently exists in Iraq. That approach would require about 28,000 support troops in addition to the 20,000 combat troops -- a total of 48,000. CBO also presents an alternative scenario that would include a smaller number of support personnel -- about 3,000 per combat brigade -- totaling about 15,000 support personnel and bringing the total additional forces to about 35,000.
The CBO went on  to calculate the costs of the troop increase, taking into account the separate estimates of how large the increase in troops would be:
If DoD deployed a total of 48,000 troops, and sustained that level for four months, costs would be about $13 billion higher than for the current force levels, CBO estimates [...] The 20,000 combat forces account for $5 billion of that cost. If the higher level was maintained for 12 months, costs would be $27 billion higher than the current level -- $11 billion of which would fund the combat forces alone. Costs would increase by lesser amounts if the combat forces were accompanied by fewer support personnel. If additional forces totaled 35,000 troops, CBO estimates that sustaining such a deployment would cost $9 billion for four months and $20 billion for 12 months.
In reporting on the CBO analysis, however, the February 2 Times article  noted only the lower estimates for the cost of the troop increase and the number of support troops that would be required:
A Congressional Budget Office estimate released Thursday concluded that sending additional troops to Iraq could cost $20 billion if the forces remained for a year but $9 billion if the forces stayed for only four months. As much as $15 billion would pay for the 15,000 support troops that the budget office assumed might be needed along with the 21,500 troops in combat units being sent by the Bush administration.
The budget office said it reached the estimate by looking at the ratio of combat troops to support troops already in Iraq. But an Army official said the estimate overstated the cost of the deployment because, with a large contingent of Army support troops already in Iraq and Kuwait, only about 3,000 support troops were likely to be required. The official said the Army did not have its own estimate of the costs.
By contrast, several other major print outlets offered readers both the low- and high-end estimates included in the CBO report. From a February 2 Washington Post article :
The Democratic dust-up came on a day when opponents of the president's policies received some unexpected ammunition. The nonpartisan Congressional Budget Office reported that Bush's plan to deploy roughly 20,000 additional U.S. combat troops to Iraq is likely to require at least 15,000 support personnel, and possibly as many as 28,000.
That could mean the plan would involve up to 48,000 troops and contractors, at a cost of between $9 billion and $13 billion for the first four months and up to $27 billion for the first year.
A February 1 McClatchy Newspapers article  provided even more details regarding the two scenarios used by the CBO:
If the additional troops remain in Iraq for more than a year, the CBO said, the cost could rise as high as $29 billion. And under traditional staging formulas, the added combat troops could require up to 28,000 support personnel, at a cost of another $12 billion through next year.
The Congressional Budget Office said the troop increase would cost more because thousands of support personnel would have to accompany those sent into combat.
The agency gave cost projections for 48,000 new troops being in Iraq for four months at peak strength and for the same number for one year at peak strength; it made similar projections for 35,000 more troops over the same periods if fewer support personnel are needed as the Pentagon claims.