Then my main point is that wealth and/or income is likely more studied than IQ, because it is/they are easier information to acquire. Even in psychology, I suspect it's quicker to assess someone's "socioeconomic status" than IQ.

The article you linked me to is paywalled. By "wealth" I mean family wealth even when one is 12 years old and have no income. The abstract says of another line of research: "Sibling comparisons ensure factors like the resources available during childhood, the impact of growing up in particular neighborhoods and genetic predispositions are all controlled, without explicitly adding these variables to the research."

If they normalize for parental wealth, then the paper you linked to concerns a different topic.