In my continued pursuit of the unbiased, I must point out that the Affordable Care Act is rather ill-conceived for its intended purpose, and likely to fail.
Republican PACs are able to use their finances to exert far more power over the general populace, and have already begun a considerable campaign to ensure the plan fails by stripping its funding (it is funded a manner similar to social security as well as by specialized taxes) -
"Sabotage Obamacare ads unleashed"If their plan succeeds, the Affordable Care Act will be left burdened with elderly and disabled recipients - i.e., those who require care, while lacking the young, healthy, paying members needed to fund the former. This will cause the plan to collapse - a failure which, when the costs of pushing the law through and then enacted it are combined, will cost well into the billions.
For a plan that is more designed to pander to the political sympathies of those who want to help the poor then to actually help the poor, that price tag is quite outlandish.
Since the current shutdown is a result of fighting over the Affordable Care Act, you can add in the cost of the shutdown to the total price tag, driving it up even further.
In total, I'd estimate about 350-750 billion dollars will have been spent on the bill if it fails by a lack of opt ins, over the bill's entire life, from policy fighting to enactment.