Sex sells! This platitude proves true especially in art history. Already a lot of Renaissance painters improved there incomes by painting gorgeous nudes or adding them to other sceneries.
In 19th century academic painting voluptuous nudes were so endemic that it was necessary to find good excuses for their omnipresence. So they were situated in mythological, biblical and not at least historical sceneries.
One of the most popular practices to place nudes in history paintings was slavery. Paining nudes on an antique slave market was not only a good excuse but also kind of politically correct. Superficially accusing the suppression and exploitation of the poor females the artists could paint gorgeous nudes and exploit them themselves by selling them in the art market.
The White Slave (1894) by the British painter Ernest Normand (1859-1923). Normand was kind of a specialist in mythological and historical nudes.
Roman Slave (1894) by the Brazilian painter Oscar Pereira da Silva (1867-1939). On the sign is written "VIRGO XXI ANNUS NATA" meaning "Virgin, 21 years old". That feigns authenticity, but it’s a poor invention. Beautiful slaves were never sold nude on the streets.
Slave Market in Rome (c. 1884) by the French painter Jean-Léon Gérôme (1824–1904). Gérôme did also a lot of paintings of this subject but preferably with an oriental setting which offered even more salacious opportunities.
In the long run nearly all these paintings are cheap exploitation already long before the word was used in that context. I know only one painting which offers another point of view on that subject: A Slave for Sale (c. 1897) by the Spanish painter Aranda, José Jiménez (1837-1903).
There is a young slave girl bowing her head in shame, clearly a victim. She’s not voluptuous like the slaves by Normand or Gérôme, she’s pregnant probably violated. Around here are the feet of lecherous men the possible buyers and above all the voyeurs. This circle can be completed with the contemplators of the painting.
Really a great piece of art!