The average Londoner is paying almost 40% of their take home pay on rent, so saving 2/3rds is already impossible.
Even as one of the lucky ones earning a top 1% salary, I _still_ pay 40% of my take home pay on a mortgage with a 33 year mortgage term!
Your idea of getting off the treadmill must be living in the countryside and taking a 80% pay cut, I suppose?
Before coming to London I was doing an equally demanding role on 20% of my current pay.
Or how about raising a family in a 1 bedroom flat? - i see loads of people doing that these days. My old neighbours both had full time well paid jobs and were still in a 1 bed with a newborn.
There's no real escape. The economy is a dog, and we are all underpaid.