In the US the legal difference between pornography and prostitution (which btw I am for legalizing) is as I have posted before that pornography is considered protected speech under the 1st amendment.
It the same concept that protects other forms of expression that might be seen as somewhat controversial like paintings of Jesus some religious groups have not liked.
The Supreme court has what they call the "miller test" to determine if something is obscene and can be prohibited.The pornography we watch does not fall into the obscene category.
http://en.wikipedia.org/wiki/Miller_test
"The Miller test is the United States Supreme Court's test for determining whether speech or expression can be labeled obscene, in which case it is not protected by the First Amendment to the United States Constitution and can be prohibited."
"The Miller test was developed in the 1973 case Miller v. California.[1] It has three parts:
Whether the average person, applying contemporary community standards, would find that the work, taken as a whole, appeals to the prurient interest,
Whether the work depicts/describes, in a patently offensive way, sexual conduct or excretory functions[2] specifically defined by applicable state law,
Whether the work, taken as a whole, lacks serious literary, artistic, political or scientific value. (This is also known as the (S)LAPS test- [Serious] Literary, Artistic, Political, Scientific.)
The work is considered obscene only if all three conditions are satisfied."
It's not about who pays who.It's about one is considered art (pornography) and one is not (prostitution).
