This map has areas of london by square foot for a closer comparison, but isn't by tube stops. Looks like we are more expensive than the bay area, if you go by area - We live in much smaller houses than in America, I believe
I've lived in both recently, and London definitely wins for more the more decrepit Victorian stock, but SF is no stranger to the flat conversion phenomenon and I'd say the average living space in the city is not much bigger than London.
However what tips the scales for London being more affordable IMHO is the fact that there is not 500 square miles of water smack in the middle spreading everything out. For instance in London I lived 9 tube stops from the center and it was < 5 miles by bicycle. In the Bay Area I also live 9 BART stops from downtown SF but it is 15 miles, I can't cycle (because no bike path over the bay bridge), and I get less for my money relative to London. Throw on the anemic transit here, and London is much more doable on a budget.
True although that's changing. London salaries outside The City used to seem to top out around £60k, but in recent years that ceiling has been broken. Meanwhile, Google and Facebook still pay ridiculous salaries, but smaller companies can't afford that, and with funding slowing down it's going to lead to even more belt tightening. You might be surprised how many people in tech are working for $50k, $60k, $70k in SF these days.
Seems like it would be more interesting in terms of price per sq ft. Some of the "expensive" stops just seem like places where the median sale represents a 4 bedroom house instead of a 1 bedroom apartment.
https://www.thrillist.com/lifestyle/london/london-undergroun...
Direct link to large-scale map:
http://assets3.thrillist.com/v1/image/1560005
Note we tend to think of flats in terms of number of bedrooms. Hatton Cross is right next to Heathrow airport, if you're wondering why it is so cheap.