Unless that study adjusted for what they did with their degree it's worthless. Rich people who go to top ranked schools often go for liberal arts in order to go into academia, teaching, or non-profit work. The project isn't to make money because they already have more than they'll ever spend.
Remember: at the top end of the spectrum (wealth and intelligence) people are still using universities for what they did a hundred years ago: to become educated, not animal training to learn a trade or make a killing. It's a completely different mindset when money is no longer an object. It colors their whole life.
The average income of my friends who grew up in rich families is a fraction of my friends who grew up in poor families. They don't view money as bad, or good, but just as there, like air. They never have had to worry about it, so income never mattered. Money isn't normative for them -- it's not a sign of effort or moral good or worth.
They are the only people I've ever met who have a healthy attitude towards money. Unlike the rest of us, they use it, it doesn't use them.
I have a friend that's trust fund rich and went to Cornell. They did build a waterfront home that was featured in an architecture magazine, but it's not ridiculously over the top. Anyway, aside from that if you ran into them outside their home you'd think they're an average middle class / middle aged person with an outdoor chic style. They drive a subaru outback and definitely didn't pick a career focused on accumulating wealth, but rather based on personal interest and an opportunity for interesting experiences.