Sawyer said that e-mails ABC News had received argued that "the Mayo Clinic is exactly the point," indicating that private companies are solving this problem, and raising the question as to why the government needs to get involved.
"And, unfortunately, government, whether you like it or not, is going to already be involved," Obama said, citing Medicare and Medicaid.
One questioner -- Marisa Milton, vice president of health care policy for the HR Policy Association, a public policy advocate for human resource executives -- said that "other industrialized nations provide coverage for all their residents" with "high quality care" without spending more money.
"A lot of those countries employ a different system than we do," the president said. "Almost all of them have what would be considered a single-payer system in which the government operates what is essentially a Medicare for all."
The president said he didn't think it wise to attempt to "completely change our system root and branch" since health care is one-sixth of the U.S. economy. It "would be hugely disruptive," he said, arguing that citizens would be forced to change their doctors and insurance plans "in a way I'm not prepared to go."
End-of-life issues were raised as well; right now it is estimated that nearly 30 percent of Medicare's annual $327 billion budget is spent on patients in their final year of life.
Jane Sturm told the story of her nearly 100-year-old mother, who was originally denied a pacemaker because of her age. She eventually got one, but only after seeking out another doctor.
"Outside the medical criteria," Sturm asked, "is there a consideration that can be given for a certain spirit ... and quality of life?"
"I don't think that we can make judgments based on peoples' spirit," Obama said. "That would be a pretty subjective decision to be making. I think we have to have rules that say that we are going to provide good, quality care for all people.
"We're not going to solve every single one of these very difficult decisions at end of life," he said. "Ultimately that's going to be between physicians and patients."
"How and who will pay for national health care system," asked Christopher Bean, who said he has good insurance with his job at Allint Tech Systems and worries about government interference.
"We will have some up-front costs," the president acknowledged. "And the estimates ... have been anywhere from a trillion to $2 trillion. But what I have said is whatever it is we do, we pay for."
The president criticized the Congressional Budget Office, which recently analyzed the cost of two Democratic Senate draft bills as costing between $1 and $1.6 trillion.
The president said the CBO "doesn't count all of the savings that may come from prevention, may come from eliminating all of the paperwork and bureaucracy because we have put forward health IT. It doesn't come from the evidence-based care and changes in reimbursement ... they're not willing to credit us with those savings. They say, 'That may be nice, that may save a lot of money, but we can't be certain.'
"We spend $177 billion over 10 years in providing subsidies for insurers," the president said as an example of the latter.
About a third of the costs will come from new revenue," the president said, pushing his proposal to raise taxes on those making more than $200,000 a year through a change in the itemized deduction in the tax code.