Why would you need to have several hundred thousand dollars in reserve if you can just get health insurance?
And even if they do cover you, from what I understand you still need to actually pay some percentage of the hugely inflated costs yourself.
I have a cousin in Florida who was charged $700 for some cortisone cream, but "good news" they only had to pay 20% because their insurance covered it! That is still $140 for something that in the UK is approx £2/$3 (three) (e.g. https://www.expresschemist.co.uk/hydrocortisone-cream.html), assuming you need to pay at all (many people get these things entirely free, and if not it will be at some fixed peppercorn price regardless of what the drugs actually are).
If basic skin creams are 700 bucks, I can't imagine what actual treatment costs. You'll want to keep a significant buffer of cash in case you are unfortunately sick one day, otherwise if you cannot pay your medical bills then I presume they will declare you bankrupt and force you to sell your house to pay the bills. The last thing you want if you have a heart attack or cancer is that your kids now also don't have a home as well as you not being there to support them etc. To me it feels irresponsible to just trust that insurance will cover you when in reality there is a not insignificant risk that you will not be covered and instead have some huge bill arrive one day that you cannot pay.
And that's why the US has thousands of medical-caused bankruptcies yearly.
Source: I work for a major insurer/provider on the West Coast.
What does happen is the hospital bills you $50 for what amounts to a bottle of Tylenol. The insurance provider says no, we only pay $8 for Tylenol, and the hospital relents and charges $8.
If you don't have insurance to call them on their inflated pricing you end up with the rather obscene bill. As an individual you have precious little pull other than, will you discount if I pay it all now? Which they usually will. This depends on having that ability, and 30% off doesn't make up for a 400%+ markup.
But hospitals have to pull a profit despite dealing with tons of regulations and non-paying patients they have to treat anyway. So as a result they bleed who they can, it's a mess.