You have a freshman level understanding of exchange rates. Let's start from the beginning with your haircut example. The beijing haircut indeed produces less va

You have a freshman level understanding of exchange rates. Let's start from the beginning with your haircut example. The beijing haircut indeed produces less value on average than the British haircut. To make the example more clear, say you're a surgeon who's performing a life saving operation. If you save the life of Elon Musk vs the life of a homeless methhead, do you create the same amount of value in the world? Even if the job is equivalent effort-skill, you have still contributed to the world more just by saving a higher-value person. I know this is morally reprehensible but we're talking economics here. Scale the example back down to haircuts. So similarly with Britain. Just because the value of all of Britain decreased, so has the value of all the work done in Britain even if the work itself didn't change. As another example, think bitcoin. If you mine for 3 hours and you get 1 satoshi the value of your 3 hours are worth different things if bitcoin was worth $100 vs $8000. In either case you did the same amount of work, the only difference is what foreigners, ie, non-bitcoiners think the value of your work is. That's how it is with GBP. So long as the currency changes are driven by real events, they matter, they matter a lot.