To be honest, I think that BA's management uses a rather self-serving phrasing when they put it that way. The descriptive phrasing would be that BA are not willing to pay for hot meals considering the costs that they are being proposed for 1 daily flight on this route. Several airlines have a single daily flight from DME (or even less) and get full catering. This includes airlines such as BA's OW partner RJ who do not fly every day. So if this is not 'reasonable' for BA while it is to others, I'm afraid that it says more about BA's than it does about DME.