It's a huge difference. As someone who's lived in the UK before: paying ~£1500 for a computer is a lot. A good software engineer salary in London is ~£60k a year, with only really good salaries going significantly beyond that (I've heard of quants and super senior people making ~£100k, but that's the exception not the norm.) That means that, if you live in the Bay Area and make a reasonable $120k, you are basically paying double for your Mac in London.

I recall at some point, some software prices (like the full Adobe suite) were so inflated in the UK that it was cheaper to fly to New York, spend a couple days there, and buy the licenses there, than it did to buy them in the UK.

We (as in, us living in the Bay Area and the US in general) live in a bubble where the iPhone is barely more expensive than other phones and Macs, while expensive, are still comfortably within our reach because our salaries are way above average.