When my wife and I visited Japan, her Tokyo-based friend came with us on the Shinkansen for the first part of our trip. If I remember right, it cost her something like $200 to ride the train to Nagoya and back. Now, that was something like 200 miles, but still, commuting via Shinkansen would not be cheap.

Edit: it was cheaper for us because we paid $250 for a 7-day Japan Rail Pass which let us ride almost every Shinkansen and almost every local train as much as we wanted. Highly recommended if you're planning a trip to Japan and want to get out of Tokyo.

Shinkansen is known as the bullet train, for those unfamiliar with the term.

Shinkansen is extremely expensive for daily commute. The vast majority of Tokyo commuters are certainly using regular trains. Also I'm sure you've seen the pictures... Let's just say, "a guy who forcefully pushes people into a full train so that the doors can close" is an actual job over there.

Elon Musk is making noises about a DC-NYC "hyperloop" with stops in Philly and here in Baltimore. Best of luck to him, I suppose - maybe in fifty years or so the Sprawl will be an actual thing.

Most of what's discussed in that article has very little to do with the main Northeast Corridor Amtrak line. It would be nice if the Acela were faster and there are various improvements slated--it's pretty much at capacity for peak times. But the decision was made when it was originally built not to go for a complete greenfield high-speed rail. It actually works pretty well most of the time. You just can't really do daily commutes from NYC to DC.

and people in megacities like greater-NY need to accept not living in a detached home.

Everyone knows it but no one will do it.