Fwiw, I live in one of the districts in the upper-right hand section. Parents here spend lots on their children, probably more than many can easily afford even on a family income that tops 100k, on academics, sports, music lessons, you name it… This begins with a decision to spend a premium on housing and continues with competitive preschool admissions, pressure to get into gifted programs and higher academic tracks in middle school and above, and to make cuts for sports teams.
Families are driven by intrinsic values, but also by college admissions and merit/athletic scholarship eligibility, and barriers to entrance set by potential employers.
When students enter public schools, it can be difficult for those whose families have not been able to provide supplemental lessons and opportunities to keep up.
Even if a well-funded public library has free programs, children access these programs only if there is an adult who can bring them and take them home. And, these (and other opportunities) are all geared towards children without special needs.
Some of this spending on children who do not have special needs indeed seems driven by fear that children will become marginalized if parents slack off, as expressed in the recent article by Neil Gabler, also referenced in another thread. Spending on special needs children (who indeed exist in these communities) is an additional issue that can get very complicated.
I am not sure that the situation of supplementary private investment in children that I see in our community is sustainable over the long run if admissions become increasingly capricious, college costs continue to rise, post-grad outcome remains uncertain and unpredictable, and family income/job security does not keep pace.