If you can't see the difference, I doubt anything I'm going to say can make much difference, but here goes anyway....
There is no sense in bringing marriage into it as an example. Marriage is a commitment between a man and woman to be husband and wife. It's his obligation to support her, sex notwithstanding, based on the marriage contract and his obligation as a husband. The fact that the coincidentally happen to have sex some times and he gives her money sometimes, is irrelevant because he is not buying sexual favors from her in a business transaction as prostitution does.
The very definition of prostitution involves selling the sex, not just having it.
Any female who just gives herself away is not a prostitute. A tramp, yes, but not a prostitute.
Prostitution, selling sex for money or favors, is NOT a victimless crime. Often the prostitutes are controlled to the point of slavery, by pimps. They can and do spread disease which can be passed onto others by either partner.
Just because there are not immediate and dire consequences to prostitution does not mean it's a victimless crime.
Metmom, I’m agreeing with you. I’m just setting out the legal position, which is what the thread is about.