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.
Agree, even though the story is probably a bit different for developers due to the difference in salary.