Of course, on $40k/year I suppose one would be taking subsidies or medicaid instead of paying full freight. But, then I guess it could be said you can make it in SF on $0/year...
No, for a single person a gold plan for Kaiser is $500/month, so $6k a year, but yes if I have $40k in investment income then I'd qualify for a premium tax credit, in this case my premium is capped to $318/month with the rest as a tax credit.
When I check at coveredca.com, I see the cheapest plan by estimated total cost [kaiser bronze] is $18069/year. Perhaps you're younger, or assuming that you will not actually have to use any medical services or products?