BA Comair luggage penalty

Great service and carrier in general; however, I would like the justification for charging R425 for an extra piece - 2 small bags totalling 22kgs would fit into one bag. Instead, the extra bag of 10kgs was the extent of the penalty. Whether manhandling one xtra piece to the equivalent justifies the extra expense, I am not convinced. And for extra space within the holding, again I am not convinced. Please inform me, BA. Otherwise, keep up the great tradition