But it's not reduced to that problem. It's just screwed by it. Even if you could build the pylons, you still need to make the tube smooth to within 2mm for hund

But it's not reduced to that problem. It's just screwed by it. Even if you could build the pylons, you still need to make the tube smooth to within 2mm for hundreds of miles. This says nothing about the overblown cost reduction. Being able to build the hyperploop at 6bn dollars implies being able to build a slower (say 200 mph) but same weight trolly on that runs on the same pylons. This seems dubious.