I always wonder with these things why the big jump in price for memory - what's the bom difference? Is the 32gb just the 64gb one with half the memory crippled?

It's £5 for the cheapest possible 32gb sdcard, about £12 retail for one I'd expect to work well. So presumably the memory is quite a small part of the cost difference -- there seems so much other tech in there, a quarter of the price can't be just memory.

School me oh gurus; is this just price differentiation?

The jump from 32GB and 64GB is definitely price differentiation. But $50 for more memory on an expensive toy isn't that bad either (or maybe Apple has conditioned me to think this way).