Basic Medicare pays for 80% of hospital costs. Medicare A&B plus a supplemental policy pays pretty much everything, except drugs, for which you have to buy a private policy under Medicare Part D.
The standard Medicare B premium is $134.oo/mth. Drug coverage starts at $22/mth and doesn’t cover a lot of drugs. A supplemental plan in Florida is about $165/mth. So, you’re looking at maybe $321/mth for complete Medicare coverage.
On top of that, you have to pay $183 annual deductible before Medicare kicks in. There is also a $1316 deductible if you are hospitalized. (Your supplemental may or may not cover that.)
It is hard to find recent figures on per capita Medicare expenditures, but projecting from 2012, the total expenditure per capita on persons 65 and over is probably about $2100 per month, including private insurance, Medicare premiums, supplementals, and funding from the US Treasury.
Since Medicare already covers the oldest and sickest people, whose healthcare expenditures are multiples of those of the younger population, and since administrative costs are much lower for Medicare than for private insurance, and since medical costs for Medicare are growing more slowly than for private insurance, the logical way to go is Medicare for all.
If the Democratic Party isn’t pushing Medicare for all as a counter to Ryan’s extremist blathering, the Dems are a waste of time.