In a bazaar you can examine the fruit or rug yourself.
An average person cannot call up $750K in a year to pay for cancer treatment. But for-profit businesses (and any organization for that matter) treat you much better if keep the carrot of another payment in front of their face. If you've forked over the whole wad of cash upfront they immediately de-prioritize keeping you satisfied.
> Most Americans don’t choose their own insurance their _employers_ do.
I don't have an employer, but I still only have one company selling health insurance in my county, so... that's all I can buy.
The insurance company has no reason to make the health recipient happy and the health recipient has little agency in pricing.