A few weeks ago, Arkansas put forward an unusual plan to expand Medicaid: It would use the health law dollars to buy private insurance for some 210,000 Arkansans expected to be covered under the program. Now, about a half-dozen states are considering something similar. The approach could end up covering millions of Americans and may win over some of Obamacare's staunchest opponents. But there's always been one big policy question hanging over Arkansas plan: How much would it cost? The Congressional Budget Office estimated last year that private insurance plans cost about 50 percent more than the public program, $9,000 vs. $6,000 in 2022 dollars.