Big financial firms with various millions in the bank in London requesting senior iOS developers also pay crap. 50-70k a year seems to be the going rate (I chatted with various, as well as recruiters). If we go with 70k its 4.000 net a month. If you want a decent 2 bedroom flat (not even mentioning an actual house) in the greater London area it will cost you easily 2000-2500. If you factor council tax + bills + transportation + etc, not much remains.

Now I know most people live outside London to save money, but you can't complain there is a shortage of talent if the senior guys aren't earning a wage that allows them to live in the same city they work in.