A £3k/month flat is certainly lavish. Or at least sized for two incomes.
(And even then, probably a nice a place in zone 1. Did that figure come from actually looking for places, or just exaggeration to make a point? I mean, of course you can spend that much and far more, but it's by no means the entry point is all I'm saying.)
I have a friend who used to rent a flat pretty much opposite Facebook's office, paid £2800/month for a 1-bed studio. Know someone else who works for a law firm in the City, he pays dead on £3000/month for a flat but he's 2 minutes away from the office and pays for that convenience. And yes, I know someone who lives in Ealing, but a 2-bed flat(not a house) is still £1900/month, and the commute was 45 minutes each way on the tube.
But furthermore, you can find 2-beds in the same location for around £2000/month (I live in one). Suggestions that an analyst at GS or an E3 at FB earning 70-100k isn't actually that well off because rents are high are silly, if they're struggling how is someone on a more normal grad salary of 35k supposed to be coping?
Our standard of housing is extremely low here. And small.