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.
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.