NYC median rent this year is $3350. That's over $40k per year. On a $100k salary, which is about $60k after federal, state, and local taxes, rent is 2/3 of the take-home pay for someone making $100k.
More concretely, if you get $60k take-home pay per year after taxes, that's $5k per month, and if you pay median rent that leaves you with $1650 for everything else, and that rent price does not include all the utilities! That is pretty hard to live on if you have dependents. If you have to feed and clothe multiple people on $1650 a month you are going to feel pretty poor, even if you don't own a car!
i think dependents are probably what drives the disconnect. COL differences per area are amplified based on family size. but this isn't spelled out anywhere, nor does the fact that most people aren't trying to raise families in major cities in the first place
Median household income in Manhattan is just under $100k [2].
[1] https://www.census.gov/quickfacts/fact/table/newyorkcitynewy...