With the Pound now trading at around $1.23, and the UK app store incorporating VAT at 20% while the US store doesn't include sales tax in the list priced, this sounds about right. Certainly the "UK premium" is nothing like the 50-100% that wasn't uncommon a decade or so ago.
Apple look simply to be pricing in the devaluation in Sterling that has occurred since the beginning of Brexit. I'm not sure anyone can find much to fault with that. The real question is how quickly Apple will move to reduce prices if/when the Pound recovers?