According to the International Labor Organization and republished by the World Bank, a woman who is forced to work as a prostitute by her traffickers can earn the pimp $67,200 on average per year.
(More under the table jobs and earnings.)
Source: Kate Transchel, “Opinion: Behind the myth of the “happy hooker”,” GlobalPost, January 4, 2010.
World Bank Source: “Human Trafficking, Modern Day Slavery, and Economic Explitation,” Johannes Koettl, World Bank, Special Protection and Labor, page 16.