What is your definition of "normal" pay? And, perhaps more importantly, what is your definition of a "normal" lifestyle??
If it's someone on a teacher's entry level salary who is hoping to live in Kensington in their own home by themselves then clearly that's not going to happen. But that's also unlikely to happen even if they earn a Magic Circle entry level solicitor salary.
It's nothing new for people to have housemates/flat mates for many years. What has changed is that people these days do seem more inclined to think that they are "entitled" somehow to live either by themselves or with a partner in a lovely non-shared home in a lovely inner city building on an entry level salary. Sadly this is being stoked by the dreaded influencers who live fake lives.
Most of the single (non-parents) in their 20s/early thirties I know of who live in the nicer parts of London who and have decent jobs ALSO have housemates. Not only does it save a heck of a lot of money, but it's also much more fun.
As for people who are living with a significant other: often times in London they will also still have a house mate or get income from a room via AirBnB depending on the situation. This isn't unique to London - I can think of plenty of friends in other similar cities who have this sort of set up.
I think people need to stop feeling so entitled or hard done by because they can't afford to live by themselves in the higher end areas of London. That's nothing new. And the situation shouldn't be a surprise to someone who has done their research prior to choosing a career or a profession. Moroever, someone who doesn't like that situation can live in a cheaper part of the country (there are many) and can - certainly at a young age - alter their career path. Heck, lots of people in middle/later age alter their career paths: there were a number of people in my law school class who had different professions before deciding to become a lawyer: one woman was in her sixties and had previously worked as research chemist. The opportunities for further education have never been more varied and easy to access. Point being: if you want to be able to afford to live in London then having rich parents or a trust fund etc certainly isn't a pre-requisite.