In April 2017, a man named Drew Calver thought he was dying. A heart attack had pinned him to the floor of his bedroom. His neighbor took him to St. David’s Medical Center in Austin, where he was successfully treated. Weeks later, he received a bill from the hospital: That’ll be $108,951.31, please. St. David’s was out of network on his insurance, and Aetna had only paid $55,840 of the total $164,941 bill for his treatment.