Cancer treatments, and pharmaceuticals for that matter, would not be so expensive if there were no third party paying for it. How do US healthcare costs compare with other countries, again?
Cancer is much more likely to hit those of retirement age than someone in a entry level job. Besides, even if a 20's something got cancer and had to pay for it out of pocket, even using your inflated figure of $200k, they could get a loan like many do with college tuition, and pay it off over time.
While relatively rare circumstances can pull at heart strings, basing a system on those circumstances is inefficient, increasing costs for all manifesting in lower discretionary spending and lower quality of healthcare.
Health insurance companies get paid, doctors get paid, politicians get paid, healthcare facilities get paid, pharmaceutical companies get paid, civil attorneys get paid. An inefficient healthcare system increases costs, yet everyone associated with it, gets paid. Who ultimately pays these costs? Even if we are not physically writing a check for own own or someone else's healthcare, we are paying for it. Still believe there is such a thing as a free lunch for tax paying working class people?
Could it be your point is healthcare is actually a free lunch for those who don't contribute to society, a group that is a critical part of the Democrat voting base?