There's no such thing as a free lunch. You can't just wish free healthcare into being. Nothing of value is free.
No one is talking about a free lunch, they are talking about a better, more efficient way of doing it.
We are saying "it is much more efficient and fair to have single payer health care"... it is not a free lunch... it is a cheaper, healthier lunch.
The rest of the developed world has _universal_ healthcare. In many countries it is provided through single-payer, in some it is through mandatory private insurance, in others it is a mix.
Where the United States stands alone is not the lack of a universal government program, but that we have many millions of people not covered by any health insurance system at all.