I’m not rich as fuck nor do I live in a dump. I don’t go out every night spending my money.
I can’t speak to London since I’ve never been there, but living in Brooklyn has been better on every metric I care about than living in the suburbs. It’s walkable. There’s stuff I want to do. There’s people.
If you’re an anti social hermit who never leaves their house then sure I guess you can live wherever. But that sounds unhealthy.