So you’d rather give power to corporations.

If the market is sufficiently competitive, yes, I trust corporations more than governments. I firmly believe giving more power to governments results in more monopolies, generally speaking, because it creates an opportunity for the larger players to lobby for ways to create barriers to competition.

That's a pretty broad statement though, and there are certainly cases where I would prefer the government to step in.

monopsony/single-payer system where all the buyers effectively are unionized

I don't think that's true. I think you're making an assumption that the payer has an incentive to reduce costs, but I really don't think that's the case. What they do have is a lot of power over pricing, and while that could be used to force producers to reduce costs, it can also be used to shift costs onto taxpayers in exchange for favors from the companies providing the services.

That's quite similar to the current military industrial complex, the military is the only purchaser of these goods, so the suppliers can largely set their prices. A monopsony means the value of making a deal is massive for a company because they get access to a massive market, which also means the value of lobbying to get that deal is also high.

So I really don't trust that a single payer system would actually work in the US to reduce total healthcare costs, it'll just hide it. If we want to actually cut healthcare costs, we need to fix a number of things, such as:

• malpractice suits - providers need expensive insurance plans and hesitate to provide certain types of care (i.e. need more tests even though they're very confident in their diagnosis)
• pharmaceutical and medical device patent system, and subsequent lobbying to set regulations to hedge against competition
• backroom deals between insurance companies and care providers where both sides get a "win" (provider inflates prices so insurance rep can report that they're getting a deal by getting a discount)
• whatever is causing ambulances to be super expensive

The problems are vast and I think single payer would likely just sweep them under the rug. We either need socialized healthcare or maximum transparency, single payer would just be a disappointment.