Many junior developer roles in London will pay 50k. Some finance ones will pay 75k or more.
600k USD / 450k GBP is also definitely reachable for a senior developer at team leader level or comparable.
Also at this level you enter into a negotiation with the business stakeholders, compensation package is tailored to each profile and opportunity.
Let’s forget that salaries in Europe are ridiculously low to focus on the handful of people who might get an extraordinary position - still paid less than an equivalent one in North America nevertheless - and pretends its doable and everything is fine.
And that's not even the top salaries, there are also jobs that pay in millions.
You'll also find similar salaries in Amsterdam, Paris, Zurich...
I'm just stating that jobs that pay the same as in the article do exist in Europe, and I don't believe they're as exceptional as you suggest.
There just is a large spectrum of salaries for software engineering, and as we all know, 90% of everything is crud, so of course the median will be much lower.