Again, there are sides to that. Paris is one of the few places more expensive than SF, and the quality of the density can be a subjective one. I for one dislike Paris and the kind of density it creates (comparable to London, just smells worse).
Not to mention London and Paris have a very good public transport system
In the Bay Area you have Caltrain and company shuttles mostly.
But yes, the SF<->SV corridor is Caltrain and company shuttles mostly.
Nor will you have people in San Francisco saying they don't want to become the next Paris.
In a lot of people's mind there's only one way to have a high population density. And they're just incorrect.