I imagine their profit margins must be greater on large packets, or something? But I wonder if they take into account the custom they lose by removing the option of buying smaller packets. It's like one of our local foodie pubs that serves vast portions. We stopped going to it years ago, since the portions were too big to eat but I was brought up to feel guilty about leaving food, and I've spoken to loads of other people who avoid it for the same reason. Yet still they do it.