You could buy a slave with a shirt in Uganda in 1872

Muteesa, the powerful King of Uganda, on the southern frontier of Unyoro, was in the habit of purchasing ivory in Unyoro for the merchants of Zanzibar. These purchases were made by an exchange of slaves, brass-coil bracelets, and long cotton shirts ; which were either of British or Indian manufacture, that arrived via Zanzibar. Muteesa, with his usual sagacity, did not permit the merchants of that country to enter Uganda in force, but he received from them both slaves and merchandise, which he sent into the surrounding countries for the purchase of ivory. He thus monopolized the trade, and kept the price at a minimum.

In Unyoro there was an established value for a healthy young girl. Such a person was equal to a single elephant's tusk of the first class, or to a new shirt. Thus a girl could be purchased for a shirt, and she might be subsequently exchanged for a large elephant's tusk. In the country of Uganda, where the natives are exceedingly clever as tailors and furriers, needles are in great demand. A handsome girl may be purchased for thirteen English needles ! Thus for slave-traders there existed an excellent opening for a profitable business. A girl might be bought for thirteen needles in Uganda, to be exchanged in Unyoro for an elephant's