Even accounting for the cost, I think many would still argue that it was worth it, replacing a highway system that divided the city with a walkable network of parks that effectively connects different neighborhoods like financial district <-> north end, along with a new series of (underground) highways that provided improved traffic flow.
Oh my God, it actually became parks?! I lived there back in 2007 or so and had no faith whatsoever that the promises that the artery would be replaced with parkland once it was finished. My apologies to the government of Boston.
Ah okay, that makes sense (but parent comment was talking about Boring Company / other new technology potentially reducing cost in the future; though I'm also skeptical).
I think the issue isn't that the techniques used for tunnel boring are so expensive, but that other issues (mismanagement, corruption) end up costing a lot. I don't think The Boring Company is going to solve those problems. Certainly reducing costs through new technology is a good thing, but it's not the whole picture by a long shot.
That doesn't look worth it at all. It cost $22 billion and the result is a narrow 1-block park through the center of Boston.
Most of those buildings next to what used to be the highway are at most 10-20 stories. A 60 story skyscraper was finished in Boston this year for $700[1].
So to a first approximation they could have had a full 2-3 blocks of parks around 15 new such skyscrapers to get the same building space after demolishing most of the buildings seen in the foreground on that picture, and have come out even on floor area.
They'd then have had had $12 billion left over to elevate the highway and put that elevated highway in a tunnel to cancel out the noise before they got to to $22 billion.
It was absolutely worth it. I've visited that area back in the early-/mid-00s when the highways and construction were still there, and recently (was just there a few weeks ago, actually) after completion. It's night and day, and the new space is a huge improvement over the old.
Comparing skyscraper build costs to tunnel build costs is meaningless.
Noise isn't the only factor. The bigger issues are division of the city, and the urban blight that is common under and around elevated highways.
The cost overruns were due to the usual things: mistakes that were expensive to correct, graft, and corruption. If you can solve those things, great. But I don't think the presence of those things should invalidate the need for truly valuable projects that make cities much more livable.
Whether it's worth it isn't measured by whether it's a huge improvement, it's obvious to anyone with eyes that the current state is better. It's whether it could have been even better had the $22 billion been spent differently.
So no, comparing skyscraper cost to tunnel cost is absolutely meaningful, because if you want to increase green space one way is to spend an exorbitant amount of money digging a highway into the ground, another is to demolish 5 blocks of 10 story houses, build one 50 story skyscraper, and get 4 blocks of public park as a result.
Urban blight around elevated highways isn't some law of nature, it's just a zoning problem, and one that's a lot cheaper to solve than digging the highway into the ground.
Those existing buildings have people inside. Pulling them out to demolish the buildings and add new, taller, skyscrapers has significant costs I think you aren't factoring in. Like all those businesses inside have to relocate... which costs money.
