A Supreme Court ruling on Obamacare expected next month could cost Georgia taxpayers billions over 10 years, according to a new analysis by the Robert Wood Johnson Foundation and by the Urban Institute.

If the court rules against the government in King v. Burwell, nearly half-million people in Georgia may lose their new health insurance — and the $17.5 billion in tax credits they would have earned, over 10 years, to help pay for it.

At issue in the case are four words in the Affordable Care Act. They say the online marketplace, or exchange, is to be "established by the states." In the end, dozens of states chose not to create their own marketplace but simply used one built by the federal government. King v. Burwell's plaintiffs maintain that the tax credits awarded to people who shop on the exchange are illegal unless the exchange was created by the state.

Tax credits are an integral part of the marketplace, since they enable lower-income Americans to afford an individual policy. In Georgia, 90 percent of exchange shoppers received subsidies to help them pay for their policies.

The new Johnson/Urban Institute study says it will cost Georgia $1.5 billion next year if the court rules for the plaintiffs. It also calculated the total federal revenue given up by the states that have neither expanded Medicaid under the law or chosen to create their own exchanges. For Georgia, the total over 10 years is $67.5 billion, the study says.