Earlier quoted context omitted.
But presumably these people are aware that there are people who aren't living on a pound a day. They can't be genuinely surprised that most people out there can afford a couple of pounds for lunch? They'd have to be ignorant of the basic economic state of the nation to be surprised by this.
I don't know: as a reasonably well paid software developer I still find the amount people are prepared to pay for lunch surprising. As the article mentions, once you buy coffee+sandwich+pastry+fruit you can easily be over £10, which is something like the price of a new Macbook every year?
I'd imagine enough people going there earn enough such that even the price of a new Macbook is not even a thing.