The other thing that BA have 'lost' in the sale and refund is two lots of credit/debit card processing fees. For a short haul flight they are not significant, but for long haul flights they can be quite a few pounds. You could argue that the cost of the original ticket includes the cost of the sale. There may be other costs that are now lost - is there an incremental cost to plate and cancel a ticket with that info being maybe available in other external systems like the GDS?