Bullshit. Apple store UK is for British people. And British people didn't get a salary raise due to Brexit, and local prices are certainly not linked to USD GBP forex. Apple store items are sold in GBP and no importing cost is involved. This is just another lame excuse to make more profit (or at least keep the same profit).
This is your argument:
"We did something dumb and our currency plummeted, but we shouldn't be held responsible for that! Those developers and that foreign company Apple should just accept less money for what they are selling. We need Apple welfare to keep our app prices from going up!"