While supply and demand affect Santa Monica as much as anywhere else, there are probably a _lot_ of people in the LA area who would like to be in SM but instead are living elsewhere, so if prices ever drop they will be sure to swoop in and grab a spot.
Santa Monica also has rent control, which increases pricing friction and raises prices (fewer people willingly moving = fewer vacancies = more competition for the few places that do come on the market = higher prices). This means that if housing drops at all people will be enticed to become buyers instead of renters.
I was lucky to get a spot in Santa Monica, but mostly because the landlord wasn't too concerned about maximizing rent, and we were the very first people to show up and look at the place. It was listed on a Sunday night and we were signing papers Monday at 9 AM. And this was in 2011!