It makes you wonder, doesn't it
I suppose you have to take into account that anything touristy is overpriced in London though.
Just looked and York Minster is £10 for an adult ticket, Westminster Abbey is £18. Birmingham Cathedral (the one on the square by the Old Joint Stock) is free, as is Lichfield Cathedral which just asks for donations, it's a stunning building and also has a collection of the Staffordshire Hoard which is also free to see.
Nice to know that they don't all charge.