The insurance system also encourages rampant abuse by companies and providers, and regulation doesn't help much. I am on a specialty medication that would cost nearly $100k/year out of pocket. I have a $400/month marketplace plan with a pretty good list of 'covered' providers and medications, but it only covers ~20% of them. However, once my out of pocket cap ($8000) is paid, the insurance covers 100% of all services.
The company that sells my medication gives me a payment card to use. I use it to pay for my first dose in January, which maxes my out of pocket cap on my policy, then my insurance is on the hook for the other ~90k and all of my other health care throughout the year. This works out great for me, I'm paying ~$4800 a year and getting everything covered with a good selection of services.
But, I can recognize why it shouldn't be allowed. The company can charge whatever they want, because the customer isn't paying any of it and the insurance company has to deal with all of it. Regulations require every policy to have an out of pocket cap, and while insurers have attempted to prevent this sort of system, many states(including mine) have legislated that they need to count payments made on behalf of the patient toward the out of pocket cap.
US hospitals also can't turn away anyone in need, so there's a relatively large expense going to illegals and immigrants who use hospitals for primary care and never pay. Some of the same issues Radial brought up are happening here, even though we don't have a one-payer system.