The usual take down here is 15 to 20 per cent off the top for graft, usual bribes, kickbacks etc. But also remember that no bid contracts go to relatives, cousins, sons in law, ex LSU football players. Now actual stealings, my guess is 10%. And to later fix what the crooked contracter did, may double the price.
I can think of less expensive solutions. Being a law abiding citizen and all, some of them are outside the range of choices available to me. But 20% of 300 bill is enough to get at least a few other people thinking.