For all those questioning the attractiveness of HSR connections, here a German example. Let's assume I am based somewhere near Hamburg and have a business meeting in Frankfurt / Main. The distance is around 500 km (a bit over 300 miles). By car, it takes me around 5 hours each way (including a toilet/ refreshing break, but excluding any traffic jam), which is above what I consider to be manageable for a one-day return-trip.
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The main problem with your example is that it neglects geography. HSR from SF to LA is geographically going to be a lot more like Milan to Frankfurt than than Hamburg to Frankfurt. You've got those California mountains to deal with plus unless you do not care about having any other stations along the way that might make use of the tracks and thus help defray the expense, you'll be detouring thru the Central Valley