Yes, they reduce costs by saying “this is what we’ll pay”, but it’s still much more costly than other countries’ systems.
My personal hypothesis is that Americans get a lot more healthcare than most countries provide, combined with higher prices. Not all of it is all that beneficial.
If you want to read something really eye-opening, check out this McKinsey report, bottom of page 14[1] It basically compares US healthcare spending across categories, adjusting for GDP (expecting the US' higher GDP means we spend more).
For inpatient care (hospital care), the US actually spends inline with what other countries spend. For long term and home care, the US spends less than other countries. Same thing with durable medical equipment.
Almost all the "excess spend" is in the outpatient setting. American's get a shit ton of procedures done that other countries just wouldn't do. Have a hernia? Providers in the US fix that, where other countries might say "we'll do something if it becomes a problem" (for example).
[1]https://www.mckinsey.com/~/media/McKinsey/Industries/Healthc...
The reason we spend so much on Medicare and Medicare is because people are less hesitant to use the service. On a per capita basis, the public payers have reduced overhead and costs compared to the private markets. If you have sources proving me wrong, I’d be happy to look at them.
And while the US market my be drowong in various regulations, it is severely lacking in price control regulation - the whole reasons for this discussion.