I have no doubt that they were exploited. Not necessarily because they were based in Africa but because they came from a position of inequality. In my career,

I have no doubt that they were exploited. Not necessarily because they were based in Africa but because they came from a position of inequality. In my career, I have worked with very over paid and not so good engineers and I've also worked with very underpaid and very good engineers from "poorer" countries such as Israel, India, China or Iran who have been highly exploited (e.g. in the US on an H1B, they are contractors that we are paying $120/hr for but it turns out they are only getting ~$20/hr). As far as the "market" is concerned, it's just arbitrage. Buy low/sell high. It doesn't matter who you are or where you come from, you will be exploited.