Railgun/MagLev requires rare earth elements to make the high power permanent magnets and it takes quite a bit of electricity to power the electro-magnets. Maglev is faster and smoother than rail - but rail is still more energy efficient and cheaper to make. The Shanghai Maglev has a top speed of 268 mph but normally goes at 200 mph.
It is about 360 miles from San Francisco to LA - about 8 hour drive by car. From San Francisco/Emeryville to LA using Amtrak's Coast Starlight. Reportedly takes about 12 hours and a one way ticket cost from $50 to $600. If you book a flight early enough from San Francisco to LAX a one way ticket will cost about $200 to 300 and a late ticket would cost about $450 (before all the other fees and taxes are piled on). A regular bullet train or Maglev would take about 1.5 hours to make the trip from San Francisco to LA.
Elon Musk's Hyperloop desigin concept is basically mating a Maglev with a pneumatic tube-like track (like the ones used by bank tellers) that would lowers aerodynamic drag forces so the top Maglev speed can be tripled (700 mph) and thereby drop the SF-to-LA time to 30 minutes.
The hyperloop's pod design is simple enough but maintaining the track could be expensive.
All this makes me think of the Simpson's Monorail episode...
Just got this from a Bing post: (This neatly ties in with Musk’s comments that the Hyperloop will be a “cross between a Concorde and a railgun and an air hockey table.”) From this article, they seem to be just guessing how this is going to be done.