From Peter Suderman at Reason:
Last year, 24-year-old Nina Dang broke her arm in a bike riding accident in the city of San Francisco. After someone who saw the accident called the hospital, an ambulance picked her up and took her to Zuckerberg San Francisco General Hospital, where doctors performed several tests, put her arm in a splint, and provided her with pain medication, then sent her on her way.
Not long afterwards, she received a bill for $24,074.50. Dang carried health insurance—but the emergency room was out of network, and her insurer would only pay $3,830.79, the rate it considered reasonable for the services she received. She owed more than $20,000.
The twist is that the emergency room is out of network for every single insurer, meaning that even people with gold-plated health insurance who ended up there could be stuck with large medical bills.