But now here's a much more critical assessment from Alon Levy, who has done an enormous amount of work on infrastructure costs over the years. He thinks the whole Hyperloop proposal is, well, loopy:
In principle, Hyperloop is supposed to get people from Los Angeles to San Francisco in half an hour, running in a tube with near-vacuum at speeds topping at 1,220 km/h. In practice, both the costs and the running times are full of magic asterisks. The LA end is really Sylmar, at the edge of the LA Basin; with additional access time and security checks, this is no faster than conventional HSR doing the trip in 2:40. ...In reality, an all-elevated system [which is what Musk proposes with the Hyperloop] is a bug rather than a feature. Central Valley land is cheap; pylons are expensive, as can be readily seen by the costs of elevated highways and trains all over the world. The unit costs for viaducts on California HSR, without overhead and management fees, are already several times as high as Musk’s cost...This alone suggests that the real cost of constructing civil infrastructure for Hyperloop is ten times as high as advertised, to say nothing of the Bay crossing. So it’s the same cost as standard HSR. It’s supposedly faster, but since it doesn’t go all the way to Downtown Los Angeles it doesn’t actually provide faster door-to-door trip times.
There's much, much more in the post, so read the whole thing.
Related: Elon Musk unveils 'Hyperloop' plans