Heretical and unromantic as this may sound, sexual relationships are best understood as a form of trade. In this view, all sexual qualities of a person are considered merchandise. Qualities such as beauty in women, attractiveness in men, and youth in either sex are considered trade values, and thus defined as merchandise. Just like sexual or romantic services, physical appearance and vitality are exchanged. These may be exchanged for similar qualities in a partner, or for emotional commitment, protection, status, or economic benefits.
This analysis does not advocate for women to become sex workers. Within this framework, indiscriminate sexual contact is argued to lower the "trade value" of female sexuality, and women with a history of undervaluing their sexuality may have a harder time securing a significant long-term commitment, such as marriage to a wealthy partner.