There wouldn't be much point in my thinking through the level of income  required to sensibly give children the best opportunities in a country I don't live in. I imagine US citizens would require much more, because the US has far fewer public services. If you look down the world rich list, the nobel prize- winner list, the people in space, the CEOs of powerful companies, Supreme Courts in any country, the recent Presidents of the US, they all had  very expensive private educations.