IMO, the basic question- aside from questioning the mega-millions that are spent before dirt is turned over- is how should the lines be built.
The US, in general, has lost it's ability to visualize massive transportation projects. Often, the 'public' primarily is concerned with how construction will interfere with traffic patterns, what noise the construction will generate, what effects the construction will have on property values, etc. This tends to produce 'micro-management' and enables property developers, among others, to have too much influence on ROW, station location, and, station design
This, in turn, greatly affects how projects are built out. Construction is done only during daylight hours, with small pieces of equipment
(I am continually surprised how many small backhoes are used in Denver's Fastrack project, for example) Projects become localized, with too much time (cost) and material spent on working on, say, a single flyover.
In Denver, the Eagle Consortium is a good first step towards constructing large public transit projects, but, efforts still are caught up from the mediocre design they inherited when they won the job bid. I suspect that despite their internal analyses (which IMO must be far better than the studies given to them by RTD) finding large style railway BUILDERS with a proven track record, outside of the major freight railroads themselves, is proving difficult. This also drives up the price, and, forces still more real estate developer and political involvement.
When I was a little kid (and I am not young now) I remember seeing interstates being built in the early '60s. Construction would literally go on for miles between cities with hour long traffic slow downs for earthmovers to cross packed dirt paths across two lane roads.
(One Sunday or holiday, I remember traveling across Nevada by car and my father telling me that there was a line of parked construction equipment a half a mile long.)
So for High Speed Rail to be built in a cost efficient manner, at least two changes have to occurr:
1st) The US has to rebuild it's network of road and rail construction companies. The network of contractors and subcontractors needs to become robust. Regretably, this can only happen by actually building projects, as the network has to be built on experience, not media or government agency hype.
2nd) The public has to accept the need to change how we transport ourselves. This can only occurr through a sharp increase in the price of petroleum in real dollars, a significant decrease in the wealth of the bottom 70-80% of the population, or a combination of both.
Until that time, the major expense will not be in construction, but, will continue to be in 'studies'. and in the political payoffs those studies entail. These studies are 'cheap' in the sense that concrete and steel cost more, but, add immeasurably to the final cost of build out.
I am confident these changes will come soon.