Where do you read a defense of anything? This is not a "weird take", just a statement of a fact (may it be true or false): that the average is ~40k and not ~15k (it is currently illegal to pay less than 15.876 euros per year).

As the other comment said, it is not a defense

But be aware that the London salaries upper tail is wider, possibly brought up by the quant firms (which are a different kind of company than most are accustomed)

levels.fyi gives 112kE as the median and 200kE/90% for London vs around 60kE for the median and 90kE/90% (pretax for both)

Levels.fyi is always very inflated for anything outside of FAANG – to the point where it's not realistic

Glassdoor lists the average for SWEs for Madrid at 35k€ vs London at £66k (76k€) which even accounting for cost of living is quite a big difference