You know, everybody seems to enjoy trashing the Big Dig as a waste of money, but I've been using it (OK, once a year, I drive through it) for the past 15 years, and I even remember trying to drive through downtown Boston on the old elevated freeway as a kid during some family trips. I've found it to be a very useful and functional. Certainly, the elimination of that ugly, disruptive elevated highway did wonders for downtown Boston. I expect that current real estate values in downtown Boston are much, much higher that they would have been had the Big Dig not been dug. Which means that the cumulative property tax revenues for Boston over that past 20 years have been much higher than if the project hadn't gone forward. I suspect that the project, over the long term, has been a net fiscal gain for the region.
Yes, it undoubtedly ended up costing more than the advertised cost, and there was some corruption and incompetence involved in the implementation. Also, it was foolish not to make provision for a future rail tunnel to connect North and South Station. But in the balance, I would say that the project was a net plus for Boston and the surrounding region.
This tendency to trash large, government funded infrastructure projects has a long history in the United States, dating from the dawn of the Republic. There was a faction in the country, consisting mostly of slaveholding plantation owners with tidewater access (Hi there, George Washington!) and coastal merchants who opposed spending public money on "internal improvements" like roads and canals (and later railroads) because their businesses had no need for these internal improvements, and, indeed such improvements opened up farmland and trade opportunities that competed with the plantations and coastal merchants. The building of the National Road (funded by the Federal government) and the Erie Canal (funded by the State of New York) were highly controversial in their day. I'm not sure how controversial the Pennsylvania Main Line of Public Works, a state-run combination canal-railroad was, but, in the end it was absorbed by a private company (the Pennsylvania Railroad), and indeed, nearly all American railroads were funded by private capital.
The attitude of private capital was summed up by Cornelius Vanderbilt (New York Central Railroad) as "the public be damned." I suspect the vested interests didn't see any benefit to public funding, because they could fund it themselves, and then enjoy their monopoly position. Of course, as we all know, if we hadn't paid for those internal improvements, our country would still be 13 dinky little states clinging to the Atlantic seaboard. On the other hand, all those private railroads gave us was the Robber Barons, monopolies, and the partial dismantling of our railroads in the mid 20th century. It should be noted that every other type of transportation infrastructure in this country, such as roads, waterways, ports, and the air traffic system was developed by the public sector, and I'm sure there's been a lot of corruption and waste on these projects over the years.