In late August, Hyperloop Transportation Technologies (HTT) announced co-development deals with Oerlikon Leybold Vacuum and the engineering design firm Aecom. The involvement of two established and publicly-traded companies was widely interpreted as validation of the idea that Tesla founder Elon Musk shared with the world in a whitepaper in August of 2013.
And there are other signs of forward motion on the Hyperloop: Musk himself is building a test track, through SpaceX, for a pod design contest slated for January of 2016. And HTT (which is not directly affiliated with Musk) is building a separate test track in California.
But not everyone’s jumping on board. The media, and especially the tech media, have been aflutter about the Hyperloop since that first paper. But close observers and transit industry vets are much less enthusiastic about the concept, from the big picture down to the nuts and bolts. They argue that even given that the Hyperloop whitepaper was a rough sketch, the most important elements of the plan — its speed and price — have been vastly oversold.
One of the Hyperloop’s critics is Alon Levy, a researcher in theoretical mathematics with Sweden’s Royal Institute of Technology, who analyzes public transit issues at the blog Pedestrian Observations . When the Hyperloop was first announced, Levy highlighted conceptual problems, including that Hyperloop’s acceleration would make it a “barf ride”.
The new partnerships haven’t changed his perspective. If anything, they’ve made him more worried about the Hyperloop’s potential to erode support for California’s high speed rail project (CHSR) between Los Angeles and San Francisco.
“I think that [Hyperloop is] reducing political support for high speed rail in certain communities, like among very techy booster types in Silicon Valley,” says Levy.
Musk has in fact been openly hostile to CHSR, and devoted the first substantive paragraphs of the Hyperloop whitepaper to a swipe at “California ‘high speed’ rail” (complete with skeptical scare quotes), which he described as “one of the most expensive per mile and one of the slowest in the world.” Musk isn’t alone in his frustrations — eminent railroad historian Richard White has suggested that CHSR could become a “Vietnam of transportation”.
And if the Hyperloop is conceptually flawed, it could end up drawing a lot of energy and support from more grounded transportation projects.
One eyebrow-raising fact is that the Hyperloop’s costs have been wildly understated. The whitepaper’s $6 billion projected cost for a Hyperloop from L.A. to San Francisco would seem to put to shame CHSR’s $60 billion (and moving upwards) price tag. But even accepting the whitepaper’s assumptions, that very rough estimate doesn’t include costs for crossing San Francisco Bay — easily several billion dollars — and the L.A. terminus wouldn’t actually be in L.A. So the stated costs are only for the very least expensive span, in the Central Valley.
There are also big reasons to doubt that the Hyperloop could ever be a transportation solution on the necessary scale. The initial plan was for pods to depart every thirty seconds, which would also be the follow distance between capsules. But the deceleration time for a pod travelling at up to 760 mph would be at least 70 seconds. To avoid a pileup in the case of one pod’s catastrophic failure, follow distances would need to be more than doubled— and passenger volume halved. That means the Hyperloop could carry only around 10% as many people as high speed rail.
Of course, ambition is inspirational, and Elon Musk has been pretty successful pursuing huge ideas. But there’s a final reason to be skeptical, not just of the technical details of the Hyperloop, but of the supposedly utopian motives behind it: It may not even be Musk’s idea.
Just a few weeks before dropping the original whitepaper, Musk met with Daryl Oster, the head of ET3 — a company that has been developing Evacuated Tube Transport for more than a decade. Oster hinted to Fast Company that Musk had actually licensed the technology from him.
ET3’s Hyperloop-like concept spent years being met not with elation, but skepticism. The fact that the Hyperloop’s reception has been so different suggests that its appeal may hinge far less on hard facts, or even big dreams, than on Elon Musk’s own growing cult of (awkward im)personality and aura of Silicon Valley superheroics. The willingness of two big companies to devote pretty limited resources to the project (Oerlikon is assigning six people) doesn’t change that math.
Sign up for Data Sheet, Fortune’s daily newsletter about the business of technology.
For more Fortune coverage of Elon Musk, watch this video: