Although ISIL (Islamic State in Iraq and the Levant) publicized an auction for slaves (captured non-Moslem women and children) in June they have since replaced that with a printed price list. Young children are the most expensive going for up to $200 each. Adolescent girls cost about $125 and adult women go for under a hundred dollars. The catch here is the buyers are restricted to ISIL gunmen, as something of a fringe benefit. The sales are made with the understanding that the buyer can resell their slave for whatever they can get. It is also understood that ISIL slave owners can try to arrange for families to ransom the slaves for whatever the owner can get (usually several thousand dollars each). The June 2015 slave auction in eastern Syria sold 42 Yazidi women who were offered to ISIL men for between $500 and $2,000. So being allowed to buy a slave is quite a lucrative fringe benefit.
Since the slaves were not Moslem they could not be married so their owners would use them for sex, housekeeping or whatever. ISIL was depending on Moslem scripture to justify this. Actually, ISIL is not alone as there is still a lot of slavery in the Islamic world. There is also a lot of hatred for non-Moslems especially those considered pagans. ISIL considers the Yazidis pagans but will enslave Christians as well. It was with Yazidis that ISIL reintroduced slavery (of non-Moslems, especially “pagans” like Yazidis) into their new Islamic State. This may appall many in the West and to placate foreigners most Arab nations have outlawed slavery, despite the fact that it still exists and continues to exist with much local support.
For example in northeast Nigeria a local Islamic terror group, Boko Haram, revived slavery in 2014. Boko Haram, which considers themselves devout religious reformers, consider slaving justified by Islamic law. Yet the Boko Haram revival of slaving resonates deeply in northern and central Nigeria. Northeastern Nigeria was once the center of an empire that grew rich by enslaving other Africans and selling them to Arab traders who transported the slaves to Arabia. This trade continued until the British colonial government suppressed it in the 19th century. Bitter memories linger and the Boko Haram slaving opened an old wound. People living in the northeastern forests report that Boko Haram conducted mass marriage ceremonies for most of the teenage girls kidnapped in early 2014. The Boko Haram men paid the kidnappers about $12 for each “bride”. This is a common practice for Islamic terrorists, especially in Africa. This enables the new husbands to justify raping their new bride and forcing her to be, in effect, his personal slave. The captured women will maintain the camp and, if necessary, carry loads if the Islamic terrorists are forced to move long distances on foot. If the military attacks the camp and some of the slaves are killed, Boko Haram can accuse the government of an atrocity.
The West African state of Mauritania still allows slavery. The divisions in Mauritania, with a population of less than four million, are between the Arab (about a third) and "former slaves" (black Africans from the south). Mauritania exists on the border between Arabs and Bantu (the ethnic group that predominates in Africa south of the Sahara). Blacks were the slaves, and slavery was formerly abolished only in 1981 but still exists in Mauritania.
In the East African state of Sudan the pro-Arab government has used slavery to encourage Arab tribes to make war on darker skinned “African” tribes. The government allowed any captives taken to be enslaved. This was unofficial as Sudan has technically outlawed slavery. There’s also slavery in Arabia. In 2010 Yemeni anti-slavery groups forced their government to investigate families living in the countryside that were still keeping slaves. At least 500 Africans are believed to be enslaved, some of them recent migrants, others the descendants of slaves.
Slavery was outlawed throughout Arabia in the early 1960s, but that only eliminated the more obvious cases in urban areas. The practice continued in more remote spaces. It's been going on for thousands of years, during which Arabs are believed to have enslaved up to 20 million Africans. As a result, up to twenty percent of the people in Arabia appear to have African ancestors and genetic studies have confirmed this. ISIL is simply being more open about a practice that is still tolerated in many Moslem nations.