The median earned income of young adults (roughly early 30s) at different IQ levels in the mid 1990s:
Extremely Bright (About IQ 135): $47,500
Very Bright (About IQ 125): $36,000
Bright (About IQ 115): $27,000
Normal (About IQ 100): $21,000
Dull (About IQ 85): $13,000
Very Dull (About IQ 75): $7,500
I created this chart by synthesizing two sources. The data for the Very Dull to the Very Bright comes from Charles Murray (see Table 2-1) who looked at the 1993 income of five cognitive classes when they were about 32 (28 to 36). The income data for the “Extremely Bright” comes from the Study of Mathematically Precocious Youth which I noticed just happened to collect data from about the same year and age group as Murray’s data, thus allowing me to extend his chart into the gifted range. The study reported that by their early 30s, mathematically precocious kids had median incomes of $50,000 to $60,000 for men and $40,000 for women. Averaging both sexes I obtained $47,500 and used this as the median for this entire gifted group.
Pinning down the exact IQ of this gifted group is difficult because they were selected at age 13 based on Math SAT scores and were subdivided into those in the top 3% (math IQ 128) to the top 0.01% (math IQ 156), but a Math IQ of 142 seems like a good estimate for the group as a whole. And since Math IQ probably correlates about 0.8 with overall IQ, I estimated their overall IQs to be about 80% as extreme as their Math IQs, thus an overall IQ around 135.