>In 1964, Japan was able to build its 320 mile long Shinkansen from Tokyo to Osaka in just 5 years for less than $12B, inflation adjusted.
Another important factor here is the cost of construction: the California project will all be above-ground, AFAIK. However, a significant portion of the Tokaido line between Tokyo and Osaka is through tunnels, so the difficulty of construction was far greater.
For a more apples-to-apples comparison, Japan is currently building the [Chuo Shinkansen](https://en.wikipedia.org/wiki/Ch%C5%AB%C5%8D_Shinkansen) line between Tokyo and Nagoya (286km/178mi), which will be a 505km/h maglev train that's 90% underground, as they have to tunnel through various mountains. It's projected to be finished in about a decade I think. Current costs have risen from the initial projection, and are at about 7 trillion yen for the first leg (Shinagawa to Nagoya), which at the current exchange rate is about USD$44B. But remember, that's about 160 miles of tunnels through mountains, plus all the rolling stock (which doesn't actually roll LOL), including the deepest tunnel in the country, and a line which isn't even conventional rail, it's a maglev track. By comparison, California is spending all that money on an above-ground train, in a place with excellent weather, using the same rail technology Japan was using 50+ years ago.
Another important factor here is the cost of construction: the California project will all be above-ground, AFAIK. However, a significant portion of the Tokaido line between Tokyo and Osaka is through tunnels, so the difficulty of construction was far greater.
For a more apples-to-apples comparison, Japan is currently building the [Chuo Shinkansen](https://en.wikipedia.org/wiki/Ch%C5%AB%C5%8D_Shinkansen) line between Tokyo and Nagoya (286km/178mi), which will be a 505km/h maglev train that's 90% underground, as they have to tunnel through various mountains. It's projected to be finished in about a decade I think. Current costs have risen from the initial projection, and are at about 7 trillion yen for the first leg (Shinagawa to Nagoya), which at the current exchange rate is about USD$44B. But remember, that's about 160 miles of tunnels through mountains, plus all the rolling stock (which doesn't actually roll LOL), including the deepest tunnel in the country, and a line which isn't even conventional rail, it's a maglev track. By comparison, California is spending all that money on an above-ground train, in a place with excellent weather, using the same rail technology Japan was using 50+ years ago.