That's odd - there is one tkt still there at £1ew, and the next band(s) would usually be £5, £7, £10 - so the jump to £12 is a bit odd. Restrictive on times tho, as you say..
I don't see less than £24.50ew - via Brum? In fact, that's cheaper than actually starting from Brum??? Bizarre!
That pesky Peak District kinda gets in the way of cross country travel...