When two people meet at a bar and negotiate a one night stand. There is no set pricing regulations (number of drinks or amount of witty banter required) or set rules (even though there may common practices these are not compulsory). The market decides value based on perceived attractiveness or level of demand (horniness). There is no guarantee even of offer acceptance based on investments made and no recourse for buyers remorse the next morning. Even stated terms and conditions can be broken ( get an std, they are married but lied, or it wasn't 8 inches after all etc). Both parties are buyers and sellers and no third party can interfere (they may disapprove or attempt to cockblock however this need not alter the deal).
Long live the free market!
Lol!