Likely not the research referenced by the GP, but this paper: http://web.econ.ku.dk/gensowski/research/Terman/Terman.pdf finds that Conscientiousness, IQ, and Extraversion are correlated with increased income (for men at least) among the Terman survey.

If I'm summarizing correctly, the Terman survey includes a group of 856 boys and 672 girls born around 1910 and selected in 1921-1922 who were followed until 1991.

Looking at that study, the high end simply wasn’t included. It seemed to just cover wage earners and professional salaried workers.

I also don't have a reference right now, but I would assume they've taken a thousand of random people and ran some statistical analysis on that sample.

Chances of someone from this thousand people being among the highest end are indeed pretty small.