It is large industry. More than one of my acquaintances got their green card and then citizenship by paying $20-$30k for fake marriage to a US citizen.
Another frame: your acquaintances were frustrated at how hard it is to immigrate and figured out a workaround. I strongly believe in freedom of movement so any legal or extra-legal means to do so are all right in my book. Rules are meant to be bent. Laws are meant to be broken.
>Laws are meant to be broken.
Those two statements sound a bit conflicting to me. Also, I don’t know how one can call green card marriage fraud “bending the rules” or a “workaround”. It is literally lying to USCIS in order to obtain a green card under false pretenses.