an unfettered organic private economy does not support them.
That's pretty silly...
there's no such thing on the face of the entire planet.
Where do you think you're going to find "an unfettered organic private economy???"
Maybe Uranus???
The point is that - remove all the government arranged revenue collections involving autos or airlines, completely privatize all of it and the economics of either one will not work out to much different a total consumer cost level than they do now. Most of what is collected now from “fuel taxes”, government tolls and transportation fees, would have their equivalents, and at equivalent or less levels from fully private operators. So, the consumer, on a per trip bases would not see much difference, only differences in who was collecting those payments and how.
But rail passengers have never seen or paid their real costs, in any combination of THEIR paying for them, not even in any rail system, high speed of not, anywhere in the world. So, in a fully privatized world, the “sticker shock” of rail transportation would find masses of customers flocking for the airplanes or their cars.
There is no rail system in the world today where what is collected from its users - in all the ways it might be collected - pay 100% just the operating costs of the system. They ALL are propped up by subsidies that are external to the system and its users - not so autos and airlines.
Remove the government and the net economics of autos and airlines won’t change much. Do so with rail lines and their users will leave in droves, except where geographic necessity makes it operationally needed.
The only currently viable COMPETITIVE markets for high speed rail, in the U.S., are limited to a few markets where population density and demand might possibly make them competitive against regional airplane routes, and then maybe still subsidized as well.
As it is now, in one of the highest capacity markets - the NY-Washington D.C. route - the round trip cost of the best rail service is greater than one can get a round trip air fare for, and so most people take the plane, because the door-to-door time-spent is less (with the take-off delays), or they take the bus because it is hugely cheaper and only slightly longer than the train (actually, the bus runs more “non-stop” than the train on that route). It is hard to see how much more costly “high speed” rail on that route will do better, unless it is subsidized even more than AMTRAK is today.