I was curious about this since it seems unlikely SF can be so much more expensive than London. When I looked into it a couple of months ago, I found zone 1 London rents are a fair bit higher than equivalent apartments in SF if you compare by square-footage and quality. I speculate that the idea SF is much pricier than London is caused by significantly lower standards/expectations for London.
Well it's needless to speculate, the variation is because London has the public transportation infrastructure to keep demand in prime areas under control. Wanting a large high quality apartment in zone 1 of London is a trio of luxuries that most people will happily compromise on, and they have the ability to do so without it being a big issue.
As far as space is concerned, in my experience one of the Bay Area's biggest problems was inefficient use of space in every which way possible. Even beyond the lack of usage of vertical space, every room I had was pretty huge, double bed, desk, room to do just about any kind of yoga I could think of and still a ton of extra on top of that. I'd have happily traded half of it for a few hundred off my rent.
I'd need to know what metrics are being used for quality (e.g. I'd take an absolute slum of a single room over sharing in prime apartment).
