When a patient arrives at Bayonne Hospital Center in New Jersey requiring treatment for the respiratory ailment known as COPD, or chronic obstructive pulmonary disease, she faces an official price tag of $99,690.

Less than 30 miles away in the Bronx, N.Y., the Lincoln Medical and Mental Health Center charges only $7,044 for the same treatment, according to a massive federal database of national health care costs made public on Wednesday.

Americans have long become accustomed to bewilderment and anxiety when confronting health care bills. The new database underscores why, revealing the perplexing assortment of prices for medical care, with the details of bills seemingly untethered to any graspable principle.

Even within the same metropolitan area, hospitals charge prices that differ by staggering degrees for the same procedures. People without health insurance pay vastly higher costs for care when less expensive options are often available nearby. Virtually everyone who seeks health care winds up paying inflated prices in one form or another as these stark disparities in price sow inefficiencies throughout the market.

While this basic picture has emerged as the consensus reality among health care experts, their evidence has been primarily anecdotal. Hospitals have protected their price lists — documents known as charge […]