I don't know about Facebook but yes, in Google's case they offer superior wages to their employees. However that doesn't diminish my original statement because

I don't know about Facebook but yes, in Google's case they offer superior wages to their employees. However that doesn't diminish my original statement because Google is likely to hire the most expensive talent and also their employees in London are paid I think about 30% less than their counterparts in the US. I suspect the American programmers are actually more effective at their jobs for a number of reasons e.g. being at ground zero when new domains open up but there is still likely to be wage gap which I'd explain by the depressed wage market in London. There are many very effective workers who ought to be paid twice or triple what they are currently earning. I know some of the younger programmers in the UK are being paid as little as 12-16k a year.