It's a simple idea, but a radical one. Let people know in advance how much health care will cost them—and whether they can find a better deal somewhere else.

With outrage growing over incomprehensible medical bills and patients facing a higher share of the costs, momentum is building for efforts to do just that. Price transparency, as it is known, is common in most industries but rare in health care, where "charges," "prices," "rates" and "payments" all have different meanings and bear little relation to actual costs.

Unlike other industries, prices for health care can vary dramatically depending on who's paying. The list prices for hospital stays and doctor visits are often just opening bids that insurers negotiate down. The deals insurers and providers strike are often proprietary, making comparisons difficult. Even doctors are generally clueless about what the tests, drugs and specialists they recommend will cost patients.

Princeton economist Uwe Reinhardt likens using the U.S. health-care system to shopping in a department store blindfolded and months later being handed a statement that says, "Pay this amount."

The price-transparency movement aims to lift that veil of secrecy and empower patients and other payers to be smarter health-care consumers. Federal and state agencies are gathering reams of price information from doctors and hospitals and posting them for the public. Health plans are offering online tools that let members calculate their out-of-pocket costs. Startup companies are ferreting out and publishing the long-secret rates that providers negotiate with insurers.