I think it goes for other industries too.  My wife who works in finance and accounting makes quite a bit more in NYC than she did in London, even for similar roles in similar industries.<p>But you may have a point in that London being the only game in town has a lot of competition among the workforce.  Also, I believe it costs much more to employ someone there and there are many more protection for employees.  For instance, it is very difficult to fire someone in the UK and it is not that way in the USA.