This month, Maryland officials estimated a long-term cost of $33 million a year to run its exchange and suggested charging carriers an assessment to join the exchange, as well as a fee on group plans sold outside the exchange, to pay for it.

The federal government plans to charge a 3.5% fee on plans sold through exchanges it operates.

The irony, Corlette said, is that by declining to run the exchanges for themselves, Republican governors are effectively expanding the size and scope of a federal government they frequently rail against.

It also means states are forgoing an opportunity to use the exchanges to improve care, she said.

In Oregon, for instance, state officials want to use the buying power of the exchange to encourage health insurers and providers to reform how they do business, bringing down the overall cost of care and improving outcomes.

States also know best how to work with community groups to reach populations that are more likely to buy off the exchanges -- the poor, the unemployed and people with limited English skills, Corlette said.

"The kind of public education campaign, the billboards and the ads and the words you use to describe this stuff, might be quite different from Alabama to Oregon or Minnesota to Texas," she said.

There are other advantages to states who decide to run their own exchanges, said Joel Ario, managing director of Mannatt Health Solutions and a former state insurance commissioner.

By running the exchanges themselves, states can coordinate regulation and enforcement of insurance plans across the commercial and exchange marketplaces.

That will likely ensure consumers are better served, particularly those who shift between private insurance and Medicaid.

But by giving the federal government control, regulation will become more complicated, making the healthcare system harder for navigate.

"That's probably in the end not as good for the consumer," he said.