It is extremely difficult to determine how much things will cost in the US system ahead of time and there is no reasonable way you can "shop" around for better prices when it comes to healthcare.
It's like you go out for dinner, but the restaurant won't tell you how much things cost, just that you should definitely order X,Y, and Z. And all the restaurants in town have the same policy. You order it, and then they mail you the bill 2 weeks later. Only for you to find out the exorbitant costs. Plus, they decided to charge you for the extra ketchup you requested.
Good luck trying to figure out what inpatient services are gonna cost ahead of time though. I work in a hospital, and a doctor asked me for data two weeks ago about what a sample set of ten of his patients were getting charged, as well as what his clinic was getting reimbursed. Took an email chain eight people long before we found someone who could actually pull the right info. Ridiculous.
Actually, it can be very easy. Quote a price prior to treatment and you are not allowed to charge more. Providers will lose money on some treatments, but on a large scale that can be predicted and rolled into the average price.
If there is a small provider, or particular treatment with high financial downside risk to the provider that the uncertainty is potentially crippling for the provider, then the provider can take out insurance to cover their loss if the treatment turned out to be far more expensive than originally anticipated.
That approach is why the $10 test costs $400. Medicaid mandates $10.01 payment, and selling it to someone for less than that is a crime (fraud). Everyone else gets a percent off of list.
If the actual cost of covering the unexpected costs is less than the margin they are tacking on, then that is simply over charging, and is not meaningfully different from the overcharging they can do anyway.
Regardless, I am not proposing a price ceiling, I am proposing determining the price prior to rendering services.