Woolhandler, like Himmelstein, is a proponent of a single-payer health system that would have the federal government insure all Americans. Both are co-founders of a leading advocacy group for that goal, Physicians for a National Health Program.
A single-payer system was not seriously debated in Congress before the implementation of the ACA. But advocates for such a scheme had argued that it would give "a bigger bang for your buck" than expanding coverage primarily through the use of private insurance, Woolhandler noted.
Read MoreMedical cost inflation at 8-year high
But until the CMS data came to light, she said, advocates could not point to official estimates of how much Obamacare would actually cost in terms of administrative overhead. If such an estimate had been available, it might have helped sway Congress to save the so-called public option for the ACA, she said.
The public option would have involved the government offering its own insurance coverage as one of the options for customers of government-run Obamacare exchanges, which currently offer only private insurance plans. The public option ended up being removed from the final ACA bill voted upon by Congress.
Woolhandler said she expects the public option, like Medicare, would have had much lower overhead costs than private insurance.
She also said that the massive amount of money that will be spent on administrative overhead in Obamacare hobbles the law's stated goal of providing expanded, affordable coverage to uninsured Americans.
"You're getting less of it if you're covering 22 percent in overhead," she said.
If the program had much lower administrative overhead costs, then people insured under the ACA could have lower co-payment and deductibles as part of their insurance, she said.
Those costs, which a customer must personally pay out of their pocket before their plan covers a medical service, can lead people to avoid seeking health care because of financial concerns, Woolhandler said.