"However, the project was completed only in December 2007 (instead of 1998), at a cost of over $14.6 billion ($8.08 billion in 1982 dollars, meaning a cost overrun of about 190%)[6] as of 2006"
Comparing a government transportation project to anything in the private sector is a canard. There's literally nothing comparable. That isn't the say that government contracting policies and processes are perfect and not abused. They clearly aren't perfect, and they clearly are abused. See the F-35, and well, pretty much every military purchase since the Cold War. See the vast majority of government infrastructure projects. Most importantly, these cost overruns aren't something that's fundamental about private-vs-public, but rather something about how American governments function.[0] Unfortunately, there's no single smoking gun, and instead everyone falls back to their favorite boogeymen. (My favorites are multiple environmental impact studies, public comment periods, fraud, and of course willful incompetence (i.e. "I don't believe the government should do this, so I"m going to do a really shitty job, and then use my poor performance as evidence that the government is intrinsically incompetent."))
[0] https://www.bloomberg.com/view/articles/2016-04-08/why-u-s-i...
The problem with infrastructure in the US is simply one of money. We don't want to pay for nice things. It's the 50 year old self-fulfilling prophesy of cut budgets, then complain that nothing is maintained and so the budget needs to be cut more because clearly it must have been wasted. Repeat ad nauseum. (This of phenomenon also plays out on the micro scale when people claim poor people are poor because they bought a stick of gum, instead of I guess investing 22 cents in an index fund or something.)