I think we need to go back to first principles here. The bond issue was sold with language that commits the State to an absolutely top-drawer, all the bells on HSR system. Nobody has ever built something like that overnite for the originally expected cost, though some places have enough intermediate traffic points (e.g. France, Germany, Japan) that they can build short independently useful segments that can later be expanded. So all this "price through the roof" stuff is hardly surprising. But not much can be done about it without placing a revision on the ballot allowing a more rational system given the probable lack of Federal funding for a long time. And placing a revision on the ballot now would effectively be abandonment.

By "revision" I'm thinking of something that gives CHSRA (or some successor) more flexibility to build track for lower speeds on a much longer schedule (Interstate system took almost 50 years to "complete" and HSR should be on the order of that) and in ways that support interim use. For instance, the Valley starter line actually could make sense if built so Amtrak and some priority freight could rent it pending completion of other segments. What doesn't make sense is to dedicate all the money to plans and testing for a big Tehachapi or Pacheco Tunnel when 1) it wouldn't be usable by anything else; and 2) the available funds from the bond issue wouldn't come near to completing construction of just the tunnel. If the speed/alignment requirements were relaxed a bit so Acela-class or high-power conventional equipment could be used, a Tehachapi crossing via Mojave would look better, though getting into the Bay Area with anything remotely resembling high speed is still an expensive challenge.

Bottom line: everybody knew (if they rubbed a few brain cells together) that $10B (minus some slices) was only enough to draw plans and maybe build a short starter segment someplace most likely in the Valley where everything's relatively cheap. Anything that will take 50 years to complete will cost 2-3x as much as the initial estimates due to inflation if nothing else, and there's plenty "else" to affect things.

What would be the "replacement cost" of I-5 from Sacramento to Irvine? In current $$ and in 2050 $$? How many Billion$? Even without much in the way of environmental shenanigans in the 50s and 60s, it took close to 20 years to complete that road. BART cost about $1B in 1960s $$ to build in the first place (and took almost 10 years to be done), and the Warm Springs extension (just a couple of stations, but with some tunneling) will cost nearly that much now. To "replace" BART now would probably approach $10B. So let's keep some perspective regarding what was promised, what's being asked for, and what things cost in the real world when you're the first one (in the US) to try it (NEC doesn't count - it's not HSR: more like a good high-end conventional railroad of which Europe has many and we have One).

Oh yes: Dan Walter's alternative for HSR? Just kill it. Great alternative ... NOT.