The price of something is dictated by one thing only: how much the customers are willing to pay. How much the customers are willing to pay is determined in part by their expectations, which in turn is determined in part by how much they paid for a similar thing in the past.

The customers in Europe and especially UK have always paid more for the same thing than their US counterparts, regardless of which side of the pond the thing was made on. How it came to be is not so important. What is important is that the manufacturers are aware of that and know that, as a result, UK customers are prepared to pay more. They have no reason not to take advantage of that, so it is not going to change any time soon.