I really hate it that you're making me defend Jolie, but even in the stories you've linked to, there's no charge that Jolie knew her son had been "purchased" nor is there any factual evidence that he was.
As I said above the adoption systems in Vietnam and Cambodia were corrupt long before her arrival, and it wasn't widely known until about the time she started her adoption process.
Since I've lived in both countries and was following these stories when they were breaking, I think I know a little bit more about it than you do.