There's a lot of this in Abrahamic scripture. The nice treatment of slaves, for instance, only applies to fellow Israelites who sell themselves into servitude. Non-Israelites can be bought, sold, kept forever, bred (and their kids are slaves too), and even killed with impunity.

Biblical scholar Dan McClellan notes that people from every age have to negotiate with sacred texts to affirm the ethos of their time and explain away those parts that don't work anymore. And this is true with all religions whether Jewish, Hellenic, Wotanic, Shinto or whatever.

So yes, in Islam, sex work is haram until it isn't.