I think the point in the article is that if your income in GBP remained stable since June 23rd, Macs in the UK have become less affordable. That is, they're the cheapest in Europe in October 28th pounds sterling, but not in June 23rd pounds sterling.

Now that may or may not be entirely due to Brexit, but price inflation is a real thing nonetheless right now in the UK, and signs are it's about to get a whole lot bigger.