The unit prices for the items of work reflect the respective bidders ( Contractors)internal production histories. Everyone pays the same for labor and equipment, the materials are the same...production is the wild card, it determines your cost. The “Profit” is the contingency you add for risk...sometimes more than 50% of you labor cost, if the job has problems and takes longer...your labor increases.
The labor in NYC is all Union, you are not going to bring in foreign workers on visa's.
How would the money not flow into the U.S. economy?
Cheers!