Once it's been shown to work it may be proof.

The track record of healthcare reforms intended to cut costs is rather abysmal.

That may be true but the first prerequisite for functioning markets is price transparency for participants. Without that it will never work. There may be other problems but you absolutely need to know prices.

Does it really need to be proved?

I'd argue that it's a mathematical/logical truth in principle, and that the only thing that requires proof is whether this particular implementation is successful at what it aims to do.