When initially announced many critics stated that the costs would be double if not more and were constantly mocked. However it cannot be ignored that it is not just the cost to build that is important but maintenance will be in the billions. Just the rail systems many cities use across the US have deferred maintenance totaling over one hundred billion dollars combined.
With regards to nations who truly have a lot of established high speed rail, while the average Japanese traveler will have nearly two thousand miles of rail travel only about twenty percent is across high speed rail. When it comes to freight less than fiver percent moves by rail in Japan with the rest by highway and other. In the US over a third of all freight moves by rail versus less than a quarter by road.
tl;dr Politicians love their legacies and reality has little input. heavy rail systems are incredibly expensive to build out and maintain
[1] http://www.latimes.com/local/california/la-me-bullet-train-c...