I've been looking around the Bay for way-cheap alternatives to the city, and nothing I've seen in Berkeley is that cheap. It seems anything close to transit is comparable to SF (at most a 10% discount).
It would seem that "far from SF" is countered by "population of monied students".
I pay $4700/month for an architecturally magnificent 5BR 2200 square foot house on the block east of the Berkeley Bowl. I suppose it's not cheap on an absolute scale, but a comparable house in SF would be $8000/month at the very minimum and in Pacific Heights or the Marina or a neighborhood I don't want to live in. I think you're underestimating the cost of San Francisco right now.
Berkeley is more expensive than Silicon Valley, but it has all of the amenities of a major metropolis (except late night anything) while being quite small in the scheme of things. It's still absolutely not a place to go for a way cheap alternative to a city, as it's still one of the most expensive areas in the USA.
Ah, there's the difference then - I've been looking at 0/1/2BR apartments in both SF and Berkeley. It seems like a decent 1BR near BART will run in the $1600-2000 range, which is in the same ballpark as most of SF.
It would seem that "far from SF" is countered by "population of monied students".