I had an accident where I had a concussion and other injuries that put me in a lot of, and the people I was with called an ambulance for me, and I wasn't really in a state to decline, but if I had been, and knew how much it would cost, I would have. The ambulance ride was, of course, out of network. As were some of the doctors that treated me once I got to the hospital. It was the first time I dealt with a major medical expense as an adult, and it came as quite a shock when the bills came several months later, that said I was responsible for about $10,000 for the ambulance (plus a lot more for the hospital), and a good chunk of it didn't even count towards my deductible because it was out of network. I later learned I should have contested that since it was an emergency, and insurance is supposed to cover out of network service in an emergency, but I was young and inexperienced with dealing with health insurance companies. Oh, and it was about a 10 minute ambulance ride.
I guess my point is, sometimes you don't have a choice, but you still end up with a massive bill. And also, that experience definitely had a chilling effect on me calling 911.