James Benedict, Anna Wilde Mathews, Tom McGinty and Melanie Evans:

To get inside healthcare costs, The Wall Street Journal looked at newly public data from one market: Boston, home to some of the world’s most prominent hospitals.

U.S. hospitals for the first time this year had to divulge all their prices under a new federal rule. The goal was to make it easier to compare prices for medical care, just as you can with flights, computers or cars.

The data reveals the wide variety of prices charged by different hospitals. It also reveals the many rates each hospital charges different patients for the same service, depending on their insurance. The rate is often highest for patients without insurance.

To understand what this means for patients, the Journal looked at one of the most commonly used hospital services, what’s called a level-four emergency-room visit—urgent but not life-threatening. The analysis focused on the amount billed by a hospital for the visit itself, not including procedures such as imaging scans or charges by doctors, which generally add to the total cost.