Now, a new study by John Hopkins researchers published in the journal, JAMA Internal Medicine shows that alerting doctors to the costs of the tests they’re ordering can lead to cheaper choices and hefty savings.

The scientists conducted a six-month experiment at John Hopkins Hospital to see if showing doctors test prices, and giving them the opportunity to comparison shop for tests they frequently ordered, would change decisions about services used at the hospital. The researchers identified 62 commonly ordered diagnostic blood tests and split the tests into two groups. Half of the tests came with their price, while the other half did not.

The researchers compared the buying behavior of the physicians and found that showing the pricing information resulted in a 9% cut in use of the tests overall and a savings of over $400,000 over the six months. By comparison, there was a 6% increase in the use of the tests without pricing information over the same time period.