These assumptions are both reasonable and allow us to focus on the major differences between the two systems. Note that under these assumptions, benefits for the elderly are more related to income than under Medicare but there are also more subsidies for the non-elderly, as in the Affordable Care Act.
A public system has some obvious advantages. The government has enormous leverage to use its buying power to secure low prices and adequate coverage for recipients. Its administrative costs per person are likely to be low, with marketing costs and profits out of the picture. Other advanced countries with public systems spend far less on health care than the US and get just as good health outcomes.
On the other hand, in a public system, innovation and efficiency might be compromised. Politics would also almost surely play a role in establishing how providers are reimbursed and benefits designed. For example, in the Affordable Care Act, evidence about what works to improve health cannot be used to set reimbursement rates for providers, and the powers Congress has given to the independent board whose job is to help control costs are strictly limited.
But what really kills the idea of Medicare for all is the fact that government budgets for health care would more than double and taxes would have to rise to European levels or beyond to pay for the expanded public system. Can anyone imagine Congress – even a Democratic Congress – voting to roughly double the size of the federal government and the taxes needed to pay for it?
One alternative is to move Medicare, which is essentially a single-payer public system, to look more like the private system used by most working-age Americans. Why should only older Americans benefit from a guarantee to health care at government expense?