A regulatory body looks at how much something "should" cost based on its history of reimbursement and the cost of its inputs and then sets a cap of say, cost + 20%.
The problem is having an independent body that is free of influence of health insurance companies and hospitals, both of which have perverse incentives to continue profiteering.
Medicines are more complicated because the manufacturer will probably have patents that grant them a manufacturing monopoly, meaning they can always set the price to whatever they want anyway. Not to mention that a multinational can afford to make less in some countries as long as on average they make enough to continue doing research. If Germany somehow sets a price that is egregiously low, the manufacturer can simply sell their medicine elsewhere instead.
The US is too big, too diverse, too whatever else, blablabla for things that work perfectly anywhere else in the world. Nothing can be learned from other countries unless it makes capitalists richer.
In reality, the legal costs in healthcare should be the next big trim on the cutting block - a single judgment for the $100 million against a provider somewhere in South Carolina makes insurers raise malpractice rates for all doctors everyone by huge percentages. Those costs put doctors out of business and all of a sudden you have far less providers in many rural areas and people die of preventative stuff. The stress of dealing with malpractice is so high (60% of all doctors are sued for almost entirely frivolous reasons, every single year nowadays) that doctors are now directing their kids to become nurses - higher guaranteed pay, you don’t lose your 20s to medical training, and no stress of career ending lawsuits.
If you go to a hospital for a longer illness and have to be taken care of by team of rotating health professionals, every lawsuit can name every single professional, whether they have anything to do with your damage or were just on the note for admitting you to the hospital. All of those providers then have to pay 100k to a lawyer to defend themselves, even though it’s obvious to a kid, they shouldn’t have to.
Medicare collects cost data from hospitals and uses it to set their DRG payments. They have the data.
You could make some law saying providers can’t charge more than X% of what Medicare rates are. You could even make it 200% (lots of room for higher reimbursement) and it would be a massive change. You won’t have one hospital charging $2000 for an MRI and another $15,000 (actual numbers I’ve seen - the payment insurers made!).
That would force hospitals and insurers to at least keep price somewhat closer to reality and they’d need to stop the game of “ill take an insurance payment below cost for X-rays but make it up in MRI reimbursment” which is what a lot of hospital do - they look at line of service finances not procedure costs (so they don’t care if X loses money if they make it up on Y).
Problem is, most hospitals have no clue what things cost (a friend worked at a major hospital and said they’ve never calculated what it costs, all in, for say an MRI).
It would be massively disruptive for a while but eventually contracts would be renegotiated and you’d end up with bills that are at least in the ballpark of actual costs.
But this is how Medicare sets its own prices - they pay a percentage of the minimum price you charge anybody else. You can't then have the non-Medicare parties charging a percentage of Medicare; that's a circular reference that could result in absolutely any price.