I think one thing they missed here is pointed out by this statement in the article: "[...] in less than two years, and, says Brandt, require fewer support pylo

I think one thing they missed here is pointed out by this statement in the article: "[...] in less than two years, and, says Brandt, require fewer support pylons. “Elon’s estimate calls for about $2.6 billion for concrete, but we’d get that down to more like $1.5 billion,” he says." The pylons aren't purely for lifting the steel, they're also for distributing the weight of the Hyperloop cars. If anything, an equal length of carbon fiber tube would be more flexible (not less) than the same length as steel and would potentially require the same number or more of pylons. The air that these cars float over does not negate gravity or the effect of their weight on the tunnel that they travel through. All that being said, it looks like our current carbon fiber pre-preg (http://en.wikipedia.org/wiki/Pre-preg http://en.wikipedia.org/wiki/Pre-preg) production is currently able to handle a construction project like this. According to Wolfram Alpha, a cylinder 9 feet in diameter from Los Angeles to San Francisco would have a surface area of approximately 52 million square feet. According to the book "Boeing 787 Dreamliner" by Mark Wagner and Guy Norris, in 2007 Boeing actually expanded the capacity of carbon fiber plants they had access to in France, Japan, and the US from 125 million square feet per year to 363 million square feet per year. I would hope that 6 years later we would be able to produce 52 million square feet.