Clive Crook repeats a common worry:
I don't question the competence of the CBO's analysts, but I wouldn't bet my 401(k) on these numbers turning out to be even roughly correct. The uncertainties lie in both directions. The plan might save more money than the CBO says: it has scored the efficiency-promoting experiments conservatively. The bigger risk is that the provisions yielding the projected savings and tax increases will be reversed before they take effect. I would need to think about it, but I might be willing to bet my 401(k) on that.
Remember, when the CBO makes a projection for how much a program will cost over time, it isn't just spitting out a single number. It's giving a range of numbers. It's typically the midpoint that you hear about, but there's always a chance that the number will be higher or lower, by a certain interval. And, in order to play it safe, CBO decided it would judge health care reform based on the worst possible estimate within that interval.