It is incredibly difficult to sustainably run a winery in California. The margins are often negative without operating at a large scale, which is part of why the industry has consolidated heavily over the past few decades.

Often times, wealthy people buy wineries as a hobby to dabble in, but end up selling and calling it a day before it drains their cash. If you want to buy wine for cheap that is made in California, buy mass-market wine.

Smaller brands are generally expensive because that price is necessary to sustain operations, but most of the time that fails, and the owners end up selling.

Not just American wine... wines from any region have always been more expensive in the US.

Quick poking around Google... Italy, France, and Germany all have mid-tier bottles of their own domestic wine for far less than we (in the US) get any wine, domestic or import.

I get the swill at a discount :) "The best wine is the wine you like best." Best deal I recently got was a few hundred bottles for under $1k, <$5/bottle. Easier than the trek to a Trader Joe's or Costco, ymmv (and I don't feel bad throwing a bottle out if it isn't for me, versus a $100+ bottle).