The best thing that could happen to people who currently have private health insurance and wish to keep it is that a public health system appears, forcing the private health insurance oligopoly to actually be competitive.
I pay (employer plus employee amounts) just under $20K/year for a family of four. I doubt anyone in the “vast majority” is paying over $50K/yr. Three orders of magnitude less than that is $50/yr. How can anyone, anywhere provide meaningful private health insurance for an individual (let alone a family of four) for $50/yr?!
A regular no-frills, some-copay insurance plan would probably cost around one to two hundred euros a year. So, yeah, two-ish orders of magnitude.
The likely amounts owed below your out of pocket maximum also have to be incorporated.
Also, my gold metal level BCBS network PPO plan is near $30k per year for a family of 4, so $20k seems like it might be sacrificing quantity/quality of in network providers.