> So it's pretty hard to look at what people are spending in two different places for two different things, with a probably large subsidy involved, and conclude that a theory about supply and demand for identical goods in a free market is wrong.
It's actually quite easy, just like you do with e.g. a McDonald's meal or a bottle of coke (e.g. the US subsidies these indirectly through corn subsidies, no other country does). It's not the same everywhere, not by a long shot, but it's functionally quite close.
Same drugs and similar are cost much more in the US.
The market is not free - it is illegal for you to have your medicine shipped from Canada or India or anywhere else.
Well, everything. Including but limited to your random assumptions, weird logic, and counterfactual conclusions.
Single payer enables the capitation model for healthcare. Lowering costs by incentivizing prevention.
Let's put it another way: it seems that you must disagree with at least one of the following statements:
(a) Higher demand, ceteris paribus, means higher prices.
(b) A single-payer system implemented in the US would likely cover more treatments than the system that exists in the US today.
(c) Covering more treatments means more demand for treatments.
(d) A single-payer system would not shift the supply curve for treatments.
With which do you disagree? It seems like most of the interesting arguments here are around (d), but there doesn't seem to be any evidence against it. Of course, again, there is some seriously massive distortion going on here, so it's hard to be sure.