They just act like brokers, how many tiers of subs later, then skim the remainder off the top. I've seen some of this in my career, hate it vehemently, because bad news travels fast. I ended up working and running a division of a company, owned by a person who unbeknownst to me, was prosecuted for kickbacks for window contracts on co-op buildings. Before I took the position, I was on a job that that the owner and his consultant played games with the buyout on windows for a high rise building, to the point I could not get them in time after approved shop drawings. I knew this window outfit, awarded them work before on a larger high rise, had them send a sample down, reviewed the specifications, testing data etc,. met the criteria and I could get them when needed. When the owner found out, he said no way, and months later while doing some research, I knew why. Morgantheau prosecuted him, it was in the Co-op news, and on the net! $2M in kick backs !!!
Worst part of it, he eventually high tailed it to china, and there was paperwork distributed for all employees to sign from the outcome of this about ethics, this and that, and eventually recording us, on the phone, giving authorization to video us etc. I'd have never accepted the position had I known. The office manager was all over me about signing this. I flat out refused, told her in front of everyone, NEVER going to happen, you can fire me and I'll leave right now, otherwise I have 65 + ironworkers to keep track off, millions in subcontracts to manage, (like $10M at the time) cranes to supervise and about another zillion things to do, you hired me based on reputation, I don't steal, lie or any of that, if my word is not good enough for y'all, stuff it, all of it, you know where. The division was closed down within 2 years or so, no traces of but one person from that company today, unreal.... needless to say, I hate any and all of those dishonest kinds of dealings with a passion!