To restate your argument: there are sometimes unpredictable health care events that arise for which one cannot negotiate, bargain, and price compare in advance. Therefore, price transparency doesn't work.
The problem is you wouldn't make this argument about any other sort of good (for example, an emergency or home car repair) because you know exactly how markets function in those cases.
The answer is: when there's price transparency, and consumers are incentivized to shop around and demand lower prices, prices come down. This benefits not only yourself, but also consumers who don't want to (or are unable to) perform this role themselves.
This is why you pay cheap prices at the grocery store even if you don't haggle, clip coupons, and so on. This is why "emergency" home and car repair (while it may cost more) does not cost an order of magnitude more than "non-emergency" home or car repair.