Karen Hao's recent book "Empire of AI" about the rise of OpenAI goes into detail how people in Africa and South America were hired (and arguably exploited) for their training efforts.
According to the book they kept dropping the rates paid per item forcing people to work ridiculous 12+ hours/day just to get enough to live on, even in the low cost of living places they were in. It was like something in a cyberpunk dystopia but real.