We're all tech workers, we all work remotely - why stay in London? Because it has nice restaurants and museums? I don't buy it. Not if you want to start a family, own a house, afford a nice car and still have some money left at the end of the day.
Besides all that, home ownership is really becoming a huge class and generational divide and house prices are rising faster outside London than within. It's only a matter of time before people in areas like you describe are priced out too.
One thing I'll say you might be very off the mark with the quarter of salary thing. Both me and my wife(also a programmer) make about 75% as much as those friends who just moved out of London.
Yes, anecdotes, I know. But I'm pretty sure tech worker salaries aren't as bad up here as people make it out to be.
Before moving to London I had offers from 2 other companies both offering numbers close to what I was on previously. Moving to London was instantly 2x their best offer.
Overall I think if you can get over the home ownership hurdle, the potential for future comfort in the city is way greater.
Did the city try not to be an asset parking for questionably acquired assets by wealthy foreigners?
Me and my partner want to start a family, but on my sole income we'll be paying ~50% of my take-home pay in mortgage + property taxes. It's probably not worth her continuing to work (although it's her choice) if we have a kid, due to the cost of childcare.
Belts will be extremely tight even though I'm well inside the top 1% income wise. That said, I still thank my lucky stars I am where I am, and can't imagine how someone on a median income feels about their prospects.