The half price Hexham to Newcastle (after 3.30pm I think) has been around for a number of years, although I didn't know it operated from other stations east of Hexham.
I did try some years ago to have it extended to stations west of Hexham but was told that 'someone' would have to pay the balance. I never did find out who 'pays' for Hexham folk to travel half price because I thought if I made too much noise about it instead of an extension to such a scheme, it just might be the death of it.
I guess it is shrouded in the history of railway ticket pricing.