23% of households in LA
10% of households in OC
9% of households in SD
6% of households in SC

That leaves 52% of the CA millionaires living in Riverside, San Fernando Valley or maybe Inland Empire?

A bit myopic.

You forgot the following not-so-poor counties which could easily contribute a few percent (e.g. 3-5%) of the states millionaires.
Santa Barbara, Monterey, San Luis Obispo, Marin, San Francisco, Sonoma, Napa, Sacramento

Throw in some rural ranchers and landowners from the other 46 counties and there you go.