There are so many absurd arguments in favor of the contraceptive mandate that it's impossible to keep up with them, but one of the sillier lines that gets repeated by the mainstream media types is the "free contraception" line.
The Obama rule outlaws the following:
(1) employer-sponsored insurance plans charging a co-pay for birth control.
(2) employer-sponsored insurance not covering birth control.
This doesn't mean "free birth control" any more than requiring employers to pay employees in beer would mean "free beer." Insurers will have to put the cost of the pills on employers and employers will put this cost on employees.
On the first point, here's an unscientific survey of pharmacy managers in which none of them said that 0-copay birth control would reduce costs by preventing enough pregnancies. So, the mandate probably adds to insurers' costs. Because this cost-hike is industry-wide, the insurers can pass it on to customers, meaning higher premiums.
What happens when employer-based insurance plans face higher premiums? Cato's Michael Cannon laid it out in an op-ed:
The Congressional Budget Office explains: “When an employer offers to pay for health insurance, it pays less in wages and other forms of compensation than it otherwise would, keeping total compensation about the same.” MIT health economist and Obama advisor Jonathan Gruber writes in the Handbook of Health Economics that economic research yields “a fairly uniform result: the of health insurance are fully shifted to wages.” In a recent survey, more health economists agreed on this issue — 91 percent — than on any other question posed
So, the contraception mandate is about replacing pay in the form of money with pay in the form of contraception, and saying that we're basically not allowed to opt for the money.