Currently, this rating system is only available to customers of insurance companies, but the company plans to make it more widely available through public search engines in the future.
Whole Foods' Mackey said competition could improve American health care, except so far, not enough people shop for that health care.
"The doctor doesn't feel compelled to compete on price," he said. "The doctor doesn't worry that he's going to lose that business to a competitor down the street. So there really isn't any price competition going on."
That's why, he said, despite their big initial savings, Whole Foods' health care costs are creeping up again.
"But if everybody was out there asking doctors what things cost, if doctors were advertising their prices," Mackey said, "we'd begin to see prices dropping."