The fact of the matter is, a lot of prostitution goes on in society. Hell, apparenly the Mall of America is having a problem with middle-class teenage girls hanging out in the hopes that older guys will pay them for sex with clothes and other consumer products.
Vice squads tend to target the prostitution that harms others, such as street corner prostitution that leads to public lewdness. Most places, vice cops tend to ignore victimless prostitution such as escort services, happy ending massage parlors and high-end brothels. Cops are realistic about this sort of thing.
If you pay some other guy to have sex with a prostitute while you watch, all three of you are guilty of a crime. Filming it doesn't make it legal.