The database also will help consumers shop around, he said.
The variations shouldn't be a surprise, since hospitals might violate antitrust regulations if they shared "proposed or negotiated rates" with each other, said Rich Umbdenstock, president of the American Hospital Association. Forty states do require or encourage hospitals to make some payment information publicly available, he said.
"The complex and bewildering interplay among 'charges,' 'rates,' 'bills' and 'payments' across dozens of payers, public and private, does not serve any stakeholder well, including hospitals," Umbdenstock said.
Consumer advocates said making the charges public is significant, even if most patients don't pay those rates.
"I think the point is to shame hospitals," said Chapin White of the nonprofit Center for Studying Health System Change.
Dr. David Goodman, co-author of the Dartmouth Atlas of Health Care, said, "It does show how crazy the system really is, and it needs some reform."
Goodman argues that hospitals should be required to go further and post the charges that patients actually pay out-of-pocket, depending on what medical coverage they have. The Dartmouth Institute for Health Policy has long found wide geographic variation in Medicare payments for the similarly ill, yet people who receive more expensive care don't necessarily receive better care. Sometimes hospitals just add tests or treatments they don't really need.
A hospital's charges are akin to a car dealership's "list price." Hospitals say they frequently give discounts to the uninsured — $41 billion in financial aid in 2011.
But some people pay full price, or try to afford it, because they don't know they can seek a discount, White said.
And even for those who do bargain, the listed charge "is the opening bid in the hospital's attempt to get as much money as possible out of you," he said.