This used to be the case, but now with IR35 rules you are generally treated as an employee for tax purposes not a business, which heavily complicates the situation. This in turn brought down expected rates to the point where most would rather the employment option since the risk of being self employed no longer came with a substantial reward.

This is becoming less true due to the current and incoming taxes that are going to rise in the UK.

Many consultant friends I know and business owners have moved away from the UK to low tax areas in Portugal or UAE.

Median pay for a dev in London is about £60-65k(a out $87,000). This isn't that high given the cost of living in the city, with your average shared flat with a few roommates going at about £1k a month nowadays. Add in that you'll be hitting the marginal tax rate of 40% plus 9% student loan tax and about 8% national insurance (ok income under 4k a month) and you don't end up with that much to live on.

The average university grad would be better off in law/finance/medicine by income in London. This isn't to stay the top software Devs don't get paid a lot, but it's a minority compared to the legions of high paid people in finance in London and the surrounding industries.

This is the very very small minority.

Jobs in London pay less than peanuts and if you earn six figures in the UK, income tax takes half of it anyway even if you go to FAANG.