Brain drain is not just about money. it is also simply about beeing able to get a life doing what we like with people alike and know how to do while beeing recognized doing it. I left my country for this exact reason, there was a culture of doing the minimum and making sure others can't organize to do great things. And trying to go back you get a lot of opposition, bureaucratic, social (jealousy and resentment is more than palpable in interviews), cultural... It is more like a one-way brain valve.