This is my question as well. I'm not only afraid of something like this happening but that I'd be ruined financially if it did (and it really doesn't have to be something this big. Simply going to the emergency room would cost me thousands).
I understand that my coverage is not all that common, although most providers do an 80/20 split. So for a procedure costing $100k (an ambulance ride and a few nights in the hospital would easily run this high) you'd have to pay $20k out of pocket.
It goes up each year (adjusted for inflation), but as an individual, your maximum out of pocket (includes everything: deductible, co-pays, co-insurance, etc) is ~$6,750.
Actually, it's the opposite. For the vast majority of insurance plans, there's an annual limit to your copay.
To be honest, if there weren't that limit there would be no purpose to insurance at all.
This is how many people are financially ruined by long-term chronic illnesses. For some less common diseases, medications can easily cost >$10,000 per month – which might not be covered by your health insurance for various reasons or only partially covered. Read the fine print.
Both my parents have suffered strokes. My father had to go to a step down unit which requires Long Term Care Insurance, something that I'm willing to bet most people aren't familiar with. Even that, due to changing regulations, your LTCI that you purchased decades ago most likely no longer covers today's prices. Unfortunately you just can't prepare for everything.