Sadly, it is an oversimplification. Maybe low IQ means a high chance to get poor, but high IQ doesn't mean a high chance to get rich. There is no IQ band in which you are most likely to earn in a $1M+ a year band, and i know a ton of quite average intelligence guys and girls who make it. If you are smart enough to finish a somewhat better than average college, becoming even smarter doesn't help you much in making more.