Yes, by almost any measure, though not uniformly:

Income: the median household income is about 1.5 times California’s and nearly double the national figure. Per capita income is nearly double the state’s.
Education: 61.5% of adults hold at least a bachelor’s degree, versus 38.1% statewide.
Home values: the median owner-occupied home value is about double California’s.

The wealth is concentrated. In Ross and in Belvedere–Tiburon, median household incomes approach $250,000, while Inverness and Marin City sit far lower. Marin City’s median household income is less than half the county’s. About 9.9% of Marin residents live in poverty.

Marin’s wealth is also heavily tied up in real estate owned by long-time residents. Many hold homes bought decades ago, with Prop 13 tax bases far below current value. That’s why Marin sees an unusually high volume of estate, trust and date-of-death appraisals.