As with most projects from that era, the environmental impact study/mitigation for such an effort today would probably cost more than the entire original project, even in real dollars, even assuming you would be allowed to build it (you probably wouldn't).
Yeah. The Hoover dam would never happen nowadays, and it has undoubtedly had some environmental effects.
Here is a fun example of how expensive infrastructure is here now:
Irvine to Corona tunnel (11.5 mile tunnel under mountains) which would connect Orange County to Riverside County: estimated 28.3 billion [1]. Both are large population centers with large economies, separated by a small-ish mountain range. They spent almost 30 million on environmental studies.
Norway made a 15 mile tunnel through the mountains for 113 million, or 0.4% of the cost. [2]
Great example... there was also an effort to expand the Tappan Zee bridge from the 1950s, adding a couple lanes was going to cost 5-10x the original iirc.
On the plus side, we have some of the cleanest air and water any civilization has ever enjoyed, so regulation isn't all bad. Maybe the Boring Company can tunnel that out for a mere $250M.
Unfortunately a lot of times those "investments" probably actually provide less value than they cost to maintain, let alone to build and maintain, particularly HSR which is generally only high ROI in a few small, rich countries with large point-to-point traffic over distances short enough that air doesn't make more sense (e.g. Japan). It's very easy to destroy value in building something.
Gini implicitly assumes a flat distribution is desirable. Ask North Korea and Cuba how that works out.
PPP GDP per capita is okay, but the PPP portion is rife with assumptions, some untenable. For instance, you really really don't want to live in a heavy industrial area in China, the air is like soup -- sometimes it pegs the AQI needle at 999. US hasn't ever had air that bad, even before the Clean Air Act.
In the US, everyone associated with the investment would have lost their shirts years ago. In Communist China, debt pays you!
The really interesting thing is that the units are mostly owned. Why? Because you can't move very much money out of China due to the capital controls, tremendous flows of money go into property -- lots of people buy real estate never intending to live in it, or sometimes even to rent it... there are actually property sales ads that suggest no one should live there as the property is not designed for human habitation. :)
