Here's a question: Dentists routinely publish prices. If you ask them how much some procedure will cost, they will tell you. If there is uncertainty, they will give you a range (e.g. to account for the possibility that complications will arise during an oral surgery). What is different in the hospital situation, apart from some rather extreme measures taken to obfuscate pricing?

> And, of course, the most expensive medical care is emergency

Is it? Or is it end-of-life? Genuinely curious to see numbers here!

> I also have no idea how it will drive down costs

Prices, not costs. The current situation is that in a lot of states there are somewhere on the order of 1-3 companies offering insurance of certain types at all. For example, for Maryland, I believe there is only one company offering an ACA-compatible PPO (everyone else has HMOs or even EPOs). See https://news.ycombinator.com/item?id=13393287 for where I got that data.

Of course in a monopoly situation there is absolutely no incentive for a monopolist to cut prices. Why would they? So to the extent that prices represent excessive profits (as opposed to the actual costs of health care), allowing cross-state insurance sales should drive them down. People who believe insurance companies are price-gouging should be _very_ in favor of removing restrictions on such sales.