I've noticed recently that smaller packets can be cheaper per kg than the bigger packs so you have to check every price tag. Even the big packs with 'bulk save' or 'value pack', etc, aren't necessarily the cheapest. Scamming bastards.

That said, with dry store ingredients with long dates, when you find a good price per kg, buy loads and stock up, whether it's one big pack or a few smaller ones!

Do this across stores, too, as you might find that rice is cheaper in one while pasta is cheaper in another.