You do it by bargaining hard with the vendors
just like everybody else does.
Mind you, you're right... the current plans don't do this because none of your politicians in Congress have the stones to actually shaft the people that need to be shafted (that is, the insurance industry) to fix your country's health care system.
Be that as it may, offering a public health insurance plan is very simple; create a wholly government owned non-profit corporation, set up the rules for capital retention for long term requirement, appoint and/or elect a board of directors, and start hiring actuaries to staff it up and figure out what the numbers need to be. Then, let them compete. Simply put, the fact that they DON'T have a legal obligation to maximize return to shareholders means that they will immediately have a huge cost advantage over everyone else, allowing them to provide better coverage for less money. Arms-length relationship with Congress makes itn unamenable to political pressure, and as they pick up customers the other insurance companies lose them... leading to the ability to use their market power to drive down costs.
If I were a business owner, and I could buy from them at the price point they should be able to offer it at, I'd be encouraging my employees to use it.
Ultimately, the public health insurance corporation should become the dominant if not the only player for the services they cover. This allows other insurance companies to work around the margins covering the "luxuries" (eg - private hospital rooms for the squeamish) but ultimately for any of the necessities the public one should be the only one covering them.
Yeah, it's socialism. So what, it works. People who are interested in using empiricism in assessing public policy outcomes should not be afraid of this. The big problem I see is that ideology is being used as cover to convince people not to use empirical methods to help decide what is the best course of action.
The best part is that there's lots and lots of empirical evidence all over the world that shows that the US system is the worst among developed nations. Foofawring about "but I don't see a plan that spells it all out for me!" shouldn't stop one from noting that everywhere else uses single-payer non-profit public insurance to control their costs and assure good outcomes, and that they all work far far better than the US system does.
