They can be, yes, but only in cities where cost of living is not driven by technical talent. For instance, downtown DC's cost of living is rapidly approaching that of SF, but engineering roles here can pay nontrivially less than those in SF because a lot of the CoL is driven by legal, lobbying, and niche defense/IC work, and most companies hiring talent aren't right in the heart of the city. General engineering doesn't have the demand to drive the price wars you're seeing in cities like SF.

I mused on SF pricing as well in a different top-level comment here, and I'm solidly convinced based on what data I've seen that devskiller's numbers here are objectively misrepresenting the current state of talent pricing in SF. Can't comment on LA, but it wouldn't surprise me if LA was similar to DC in that CoL has skyrocketed because of other inflows of liquidity, e.g. passive income through the entertainment industry.