Because they can!
You all want to know why they can charge so much for exams (and flight testss and license issue for that matter!). It is because they can! Who else in the uk is going to let you loose in the air? No one! They have one of those niche markets that no other operator can get into. I think they are just trying to raise the hoops for s%&*s and giggles to see how high we can jump. A bit like the olympics just more expensive and not as funny for us. Its funny though, I was being mocked by my cpl instructor today because my Antipodean CAA issued me with a piece of laminated paper (license) when over here you get a big 'novel' of a license. They thought it was hilarious and might as well been drummed up by any old hack on the family pc. I pointed out that it cost only $50 for the issue not £340 , the flight examiner verified your hours and the license was back in your hands within a few days.
You want to know why the CAA can raise prices. Because they can, its wrong and everyone cant understand what our money goes towards but thats not the CAA's problem!