Do you have any evidence or are you just pulling this out of thin air? All sources I can find estimate pre construction costs between 3 and 10% depending on type of infrastructure and where it is (the US according to [1] is on the lower end with 3-5%). To put this in perspective the profit margins on construction projects is 7% according to [2], which also does attribute skilled labour shortages as the main factor behind increasing construction cost.
[1] https://srgexpert.com/wp-content/uploads/2023/07/The-cost-of... [2] https://publications.turnerandtownsend.com/international-con...