Because that is reality. $65k is where the richest quantile for neighborhood median household income starts, by census tract [0]. The linked report was compiled by Dr. Shanea Watkins, a policy analyst specializing in empirical studies.

Unless you have sources that claim otherwise, my original claim stands.

[0] http://s3.amazonaws.com/thf_media/2008/pdf/cda08-05.pdf

Or that just means that upper class doesn't start at the boundary of the top quantile.

I'm sorry but no stretch of the imagination has upper class as a couple making 33k/yr each. That's absolutely absurd. That's $16.50 an hour with no overtime.

Looking at it, upper class typically is the top one or two percent of the population.

https://en.wikipedia.org/wiki/American_upper_class

The OP specifically mentioned "upper classes". It is a fact that the lower classes (lowest quantile) are underrepresented, and the higher classes (highest quantile) are overrepresented [0].

[0] http://s3.amazonaws.com/thf_media/2008/pdf/cda08-05.pdf

That's not absurd - if you define "upper quartile" to be so broad, you get the conclusion you want - that they're "overrepresented".