Monorails are expensive only when they are constructed at ground level, or below ground. Not above ground.
Above ground, monorails are a more affordable option than normal trains.
When putting into consideration the limited space, and mass populations of Santo Domingo and Santiago, the above ground monorail is the most logical, and fiscally responsible option for modernized public transportation.
They are more sexy, and are
not less expensive, as Right of Way is about the same, and the old fashion duorail beds are quicker and way cheaper than thousands of columns and beams for a straddle-rail system. I am sure a suspended system is not being proposed.
Also you can not use crossover track switching, meaning you need two for two way traffic or it is a one way loop.
Plus they can't carry the freight loads.
Yeah monorails got popular and maglev monorails are super sexy but require high tech maintenance.
Syndey, Australia abandoned their monorail for poor service record after about 20 years.
they have one advantage in that they eliminate cross traffic conflicts but that could be done on duorail bridges
I applaud anything that could de-congest Santo Domingo and Santiago - since those cities are choking.
In any even I suspect most of the posters here will not be alive to see it come to fruition, but it's nice to have dreams.