I have a friend who won a contract to do some work at Monterey County airport.
AFTER the work was done, he received notice from some government agency (it's been 10 years or so, so I don't remember exactly who), that he would have to go back and pay his employees prevailing wage for the work they performed. He was paying them something like 20 dollars an hour plus meals and lodging.
He had to go back and pay them something like 50 dollars an hour plus per diem and other such perqs.
Long story short, he ended up losing money on the project.
If he bid the job on an RFP that indicated no requirement to pay prevailing wage and/or the project didn’t utilize federal funding it should have been easy to invoice for the additional PW costs and associated overhead.
If he didn’t catch that it was in the RFP then he was SOL...