project                     $million/mile  persons/day
  LA Red Line                 259 [1]        140943 [1]
  MARTA heavy rail (estimate) 200
  I-64 highway                 53.5 [2]      140000 [3]
  American Maglev (estimate)   20

That would imply that the US has several trillion dollars invested in its highway system, correct? Does that number pass the smell test to you?

Wiki reports that our ~45,000 mile interstate highway system cost about 425 billion, or a hair under $10 million a mile, in 2006 dollars. That's under a twentieth of what the LA transit folks are quoting. (I think they're doing creative accounting by reclassifying part of construction as operating expenses, which is a frequent trick in this field, but I've got nothing to back that up.)

http://en.wikipedia.org/wiki/Interstate_Highway_System

If I commuted by car I would've personally paid a hell of a lot more for the privilege. The up-front cost of the infrastructure is not the only consideration...

This does not speak to operating costs.

Mass transit fairs are usually subsidized from general tax revenues - user fees usually cover something like 10-25% of actual costs.

You don't just pay for gas, you pay for the car to put it in.