From that paper's conclusion:
The results confirm other researchers' findings that IQ test scores and income are related. Depending on the method of analysis used and specific factors held constant, each point increase in IQ test scores is associated with $202 to $616 more income per year. This means the average income difference between a person with an IQ score in the normal range (100) and someone in the top 2% of society (130) is currently between $6000 and $18,500 per year. While income and IQ test scores are related, results do not suggest a link between IQ scores and wealth. Regression results range from a negative to a small positive relationship depending on the specific analysis done. Moreover, since most of the statistical results are not distinguishable from zero, this suggests IQ test scores and net worth are not connected.
What exactly does cause the concentration of wealth is an interesting question, but it appears to be more complex than simply making more income, and unlike income doesn't appear to be as strongly associated with intelligence (if associated at all).