Excellent point. I once read that they could put a state of the art maglev train from DIA to Breckenridge, but that it would never be done because the price would be too high at like 1.5 billion. In other words, for the price of a fighter jet program that we don't need and that doesn't work, we could have had about a thousand such trains.
Well, the problem with ideas like Maglev and monorail is that such systems are totally untested for the operating environment in question.
The I-70 corridor is steep to a degree that is really problematic for many high-speed mass-transit options. For conventional rail, you only have to look at the Georgetown Loop Railroad to get an idea of the constraints- and that was a 15 mph narrow gauge line.
If you aren't ceaselessly making slow-speed loops, you are looking at 8% grades, which to my understanding is both untested territory and would require massive amounts of energy. Ditto for monorail- that kind of grading is off the reservation.
I don't think it makes financial sense to be the test subject pushing the theoretical limits of all of these technologies by way of grading, altitude, snowfall, etc. There is a reason a railroad has never been built over the divide there, and it is really difficult for me to take cost estimates of such a boondoggle seriously because nobody really knows what it will cost and overruns should be expected.