There's also been considerable price increases in the Fresno area, too (though it's still possible to purchase brand new homes there under $400K), which is outside the normal Bay Area commute orbit, though now with WFH, an occasional trip from Fresno to Silicon Valley or San Jose isn't that bad. The only places I haven't seen dramatic appreciation in house prices are smaller, more isolated metro areas that haven't attracted those leaving the Bay Area or Los Angeles, such as Hanford and Visalia.
Coming from a guy who grew up in Sacramento, yes the Central Valley is hot, but the best part about the Central Valley is its relative affordability and its proximity to many interesting places. Portions are close enough to the Bay Area to commute (though I wouldn't do it every day), and while it's farther away from the beach than the Bay Area, it's closer to the Sierra Nevada mountains, and SoCal is still within weekend-trip range. Living in the Central Valley allows people to take advantage of California amenities without having to get on a plane or take a very long road trip (though, admittedly, Reno and Las Vegas are also close enough to many of these same California amenities, sometimes even closer depending on your destination).
EDIT: There are some other cheap parts of California. Many of the desert areas of the state are affordable. Lake County, north of Napa, is quite cheap.