From http://voi.org/books/mssmi/ch10.htm


Mahmud of Ghazni carried away large numbers of captives from India in every campaign and sold most of them. Jayapala the defeated Hindu Shahiya King of Kabul was publicly exposed at some slave market in Khurasan by the order of Mahmud who “commanded that he might be ransomed for the sum of eighty dirams”. Raverty suggests that “the word ‘thousand’ must have been left out. If not, Mahmud did not set much value on his captive.” As Jayapala was old, the price he could fetch in open auction probably could not be more than 80 dirhams. Or, as Hodivala points out, the object of exposing Jayapala to public derision was evidently to compel him into surrendering to his victor’s demands and purchase his release on his captor’s own terms, which was fixed at “200,000 golden dinars and 250 elephants; and the necklace taken from Jaipal was valued at another 200,000 gold dinars.”  Therefore, 80 dirhams as the price of an old king signifies nothing.

In one instance specifically Al Utbi gives an idea of the gain from the sale of captives. According to his narrative, Mahmud, after his campaign in Mathura, Mahaban and Kanauj (1018-19), returned to Ghazni with, besides other booty, 53,000 captives and each one of these was sold for two to ten dirhams. From this statement it would be safe to infer that the lowest price at which an Indian captive was sold was two, and the highest ten dirhams. It would also be safe to conclude that slaves were captured by invaders to be sold to make money; for Utbi adds that “Merchants came from different cities to purchase them so that the countries of Mawarau-n-nahr, Iraq and Khurasan were filled with them”. Earlier, in the expedition to Thaneshwar (1015), according to Farishtah, “the Muhammadan army brought to Ghaznin 200,000 captives, so that the capital (Ghaznin) looked like an Indian city, for every soldier of the army had several slaves and slave girls”.