First of all, that was the same story used to sell interstate highways. It is a fragile infrastrucuture, however, because disrupting any number of things (wires, tracks, bridges) at any point on that route makes it useless. Military trucks can generally traverse anything but a blown out bridge.
Secondarily, Im going to cite an example- an MCI line haul bus costs a tour company about $350k including restroom. It costs NJT, sans Restroom but with cosmetic stainless cladding, about double that.
We use union labor, and that means that the workers need to be paid a living wage + for a country with somewhat higher standards of living. We have much more costly property seizure proceedings, we have a lot more lawyers, and much larger and more powerful NIMBY base, not to mention safety standards that certainly are higher than the Chinese, and are based on the fact that we are too dumb to consistently keep trains on the tracks, and to stop them from occupying the same space at the same time.
All of this means that it will cost our taxpayers several times as much to build the thing. Possibly even an order of magnitude. So citing cost really isnt as unreasonable as you make it sound.
If you want to advocate for something, dont just look at your perceived advantages of its existence. Also look at the positions that can and will be taken by people who oppose it. For example, I like the idea of HSR, and I generally dont like NIMBYs, but I dont want the thing wooshing by my house. If you are going to build it near my house, I better not hear it (sound barriers or dont!).
Various parties who have vested interests in preventing this stuff (oil companies, air lines, and so on) they have a bunch of verbiage they trot out when this stuff comes out to start a counter movement. Discounting the reasons of these campaigns as stupid and antiquated may be an automatic response, and logical in your mind, but those opposed have equal logical certainty of their perspective.
Pick half a dozen issues you dont give a hoot about and listen to arguments from both sides- it doesnt matter what issue. You will realize that the logic and reasoning of both sides is at least somewhat wrongheaded, and both sides arguments are downright dumb.
These kinds of discussions are almost always counterproductive; we have two sides of this argument here: old fashioned and fiscally conservative Railfan who think this is both too expensive and likely to kill their beloved rail travel experience, and the more progressive, less fiscally conservative transit advocates who want to see more transit options. And each one sits I here, makes arguments the other side will never agree with, and then preaches to the choir of their side.
Enough of that, already.