Amazing collection! I tried to do this on a much smaller scale years ago, categorizing them in orders of magnitude: futureblind.com/p/the-s…

I was also thinking along the same lines for measuring the size of the project, getting to: "Man-years + Value of Raw Materials (possibly in ounces of gold)". Dividing project cost by GDP/cap is great proxy.

I wonder if it would be possible for a historian to chime in and get good estimates from very old megaprojects like the pyramids or the Great Wall of China.