I heard a story about the highrise developments in downtown Dallas; that young people and empty nesters - who work for TI and other suburban companies - live downtown and use Dart to get to work, instead of living in the burbs and going downtown to work. This, Dart trains, is part of the reason we have 19 cranes building new housing and that, taxes on construction and homes (starting @ $400,000), helps to offset that per person cost you mention.
If they had built the Monorail in the median strip of Las Vegas Boulevard, it might have worked. Instead, the Monorail is so far from the Strip that nobody wants to make such a long hike.