That Sydney Metro tunnel is coming in at nearly double the initial budgeted cost. It's over $1B per km of tunnel. Australian infrastructure projects are hardly something to be proud of.
The fact is that megaprojects basically never come in anywhere near their schedule or budget. That's because of a selection bias. When you crunch the numbers honestly, megaprojects come out as a terrible on a cost-benefit or ROI analysis. The ones that get built are built by people who choose to ignore the honest figures in favour of the shiny, optimistic ones. Et voila, another farce.
There are lots of other factors, but that's the core one that precedes the others.
Houses typically go according to plan because so many of the processes and parts are standard. Even large mansions can go according to plan if you have good management (note that cheap management is rewarded for change orders and thus will ensure things don't go according to plan while better management will see that if they don't make a minor change now things won't go according to plan latter.
We do have ships, rockets, and a few other things that don't need wheels (tough they tend to have wheels of some form inside), but the wheel itself is still just incremental improvements on that first one way back...
[0] Best example of this sort of logic that I have seen implemented is painting the golden gate bridge, just one properly sized and experienced crew painting from one end to the other and back again without the boondoggle.
Otherwise every 20 years they would need to hire, train, then fire 200 painters for a 6 month-long paint job project. 200 painters, managers, and etc. who will invariably be less experienced with the finer points of painting said bridge since they don't do it every day.
The Project Production Institute take a similar view: that instead of modeling a project as a fixed thing, you focus on it as a production process.
That's before adding other factors such as increase regulation, inflation and good ol' corruption.
If all the businesses along the block you are trenching through back then went under... so fucking what?
If your 24/7 jackhammers kept all the block up the whole night you’d tell them to take a hike.... etc, etc, etc.
If turns out if you care about any or all of those things, your costs go up. Back then it was all just negative externalities that got foisted on the neighborhoods around them. Think of the negative externalities causes by our interstate highway system. Good luck building that now! It literally divided entire neighborhoods. The entire thing would be require to go into a tunnel under the city. No way would people tolerate that shit now.
https://en.wikipedia.org/wiki/Second_Avenue_Subway#Construct...
It seems that China does not suffer from this "cost disease", but I don't know any real facts.
We also have more complicated, and are dependent on, soft and hard power structures to access and use capital. A great place to start looking into these issues is Bent Flyvbjerg at Said, Oxford
[0] http://nymag.com/intelligencer/2019/05/new-york-infrastructu...
It has been my experience -- which some more "keepin it real" journalism concurs with -- that New York's outlandish infrastructure costs, as well as the majority of the USA's public projects, are primarily due to two main agents:
1. White collar bureaucracy
2. Blue collar "bureaucracy"
Both parties -- and the multitude of agents that operate within them -- are all too able to align their "piece" of the project towards their own interests.
These interests very much involve time and money.
For money, it's simply rerouting costs. And for time, it's "making one's mark," by misallocating resources to personally-enriching matters, that do not benefit the project as a whole, and usually hinder it.
It's late, and I'm not at 100% to go into detail, but surely this is well-known already?
I take the argument about selection bias from Brent Flyvbjerg, who has been studying megaprojects for a fair while now. He calls it "survival of the unfittest"[0].
A similar resource is Merrow's Industrial Megaprojects[1], which is based on a large dataset of such efforts. He identifies many factors in project overruns, but essentially notes that most projects start off with fanciful estimates that will never be met. For a book about petrochemical plants, bridges and power stations, it's a fun read.
[0] https://arxiv.org/ftp/arxiv/papers/1409/1409.0003.pdf
[1] https://www.amazon.com/Industrial-Megaprojects-Concepts-Stra...
https://www.nytimes.com/2017/12/28/nyregion/new-york-subway-...
https://www.smh.com.au/national/nsw/under-wraps-sydney-s-fir...