Back in 2013, @bkotsko posted a demographic survey in the old Alden thread. The results and following comments start here. I think the design of the survey underestimated income levels, and the "and up" value should have been higher than $300K to get a more accurate distribution.
Anyway, it's one take that may help answer your question. (regular disclaimers apply: who volunteers to take an income survey, how significant is n=87, internet self-inflation, as some suggest...)
Thanks for the reminder, @Alpina
Although I am sure the demographics have changed, the results were definitely interesting.
I agree about some of the shortcomings. (income, self inflation, etc..)
The n=87 was a fairly good spread of Alden forum participants.
I am sure it could be expanded.
It would be great if someone revamped it and followed through with a new survey.