Another one to add to the list!
I know of a lot of tickets like this. Some of which I don't advertise much because some TOCs do take pleasure in finding such anomalies and removing them, and some do read this forum! The easiest way for them to do this is putting the price up for the tickets that are cheaper, other ways would be to change the Routeing Guide (not so easy) or to request for a "negative easement". They rarely put the price down for the tickets that they have raised to be too expensive.
It is very rare that I buy a ticket from my origin to my destination. I usually either by a combination of tickets, or buy further. This is because it is rare that a ticket from origin to destination is the best value, due to the nature of our ticket system.
A ticket from York to Doncaster returning another day is more expensive than a ticket to a couple of stops after Doncaster. It didn't used to be so. Privatisation has caused many anomalies to be created (over time), and "simplification" resulted in even more!