She did check out her options through New York’s marketplace but said she was not impressed. She did not qualify for a subsidy based on her 2013 income, she said, and was particularly put off by the high deductibles on many of the plans available to her.

With an income that fluctuates unpredictably, she said that she could not justify a new expense for something that was “not a priority.”

“It doesn’t scare me not to have it,” said Ms. Reinberg, adding that she exercised, ate healthily and rarely got sick. “I’d rather pay down my credit cards than take on another bill for something I don’t know that I’m going to need.”

She acknowledges that she could have major medical expenses as she ages. And she might buy insurance in the future if her income stabilizes, she said. But for now, like many others, she has decided that the financial penalty for not buying insurance is more palatable than the cost of premiums and deductibles.

“I know what the penalty is going to be,” she said, “and I can get my head around that.”

There is no demographic data on the uninsured who could have bought coverage through the exchanges but chose not to. But a federal report last year on the overall uninsured population eligible for coverage under the new law estimated that 45 percent had incomes low enough to qualify for financial assistance buying exchange plans. Many others were poorer and eligible for Medicaid because their state opted to expand the program. Another federal report last year said that young and healthy people made up nearly half of the uninsured, and that more than half were men.

For Mr. Huber, the salesman, the complexity of the process was enough to make him give up trying to enroll.