To answer an earlier point, maybe food is not essential on a shuttle flight, but if that is the case and catering is degraded, then tickets should be cheaper.
With EDI to LHR, the ticket (fully flexible) cost is truly too much, and most travellers on this route are aware of the fact they are being ripped off. Every now and then BA or BMI get the wheeze of an idea to degrade the food given, but don't cut the ticket cost - that's all.
Most people using this flight route on expensive tickets are in industries where pre booking or the lack of punctuality etc of budget airlines is of limited use. So they have to put up with rip off fares.