I think government as a single payer inevitably involves price controls and other restrictions.
So you agree that it would not be impossibly expensive. Good
Now, the argument that there would be price controls and restrictions, is not founded in reality. Most Americans have stricter restrictions on their healthcare programs (being it Medicare or a Managed Health Care system) than the Universal Health care systems in Canada and even more so in Western continental Europe.
It is likely easy for a smaller country to initiate single payer and lower prices without impacting the overall quality vis-a-vis the United States.
Sure, it is easier for a smaller country, but then again economies of scale should favour a bigger country.
Don't forget that USA is the worlds leader in management of big organizations (one example is the military).
Without boast, U.S. citizens pay the freight on many drug and medical device breakthroughs.
You will have to provide some data to prove that claim. While Medications are more expensive in USA than everywhere else, I am not sure most new medical developments are done in USA.