Here is a basic fact of health care in the United States: Doctors and hospitals know what they charge, but patients don't know what they pay. As in any market, when one side has no information, that side loses: price secrecy is a major reason medical bills are so high. In my previous column, I wrote about the effect of this lack of transparency on the bills patients pay out of pocket. We know about these bills, which hit us directly. What most people don't know, because the costs are hidden, is that the same imbalance exists with insurance. The employers and employees who buy health coverage have delegated vigilance over health care costs to insurers — but insurers, for the most part, have gone AWOL.