Whatever the reasoning behind this, this is reason why I carefullly look at the unit pricing, check bulk packs of products against small packet of the same product. I estimate 10-20% of our fornightly groceries contain products where the bulk packaging is greater in price than their smaller packaged equivalent.
I have overheard and politely pointed out to other shoppers in the aisles of this anomoly when I hear their discussions on automatically taking the bigger, bulkier packaging.
Soft drink is notorious for this practice also.
As Barry has stated, to work out what products are more economical to purchase, it's simple primary school maths, and I honestly think most shoppers either don't take the time to work it out, or cannot!
In my opinion, a lot of effort and $$ goes into clever marketing tactics. Let's be honest, they are to make money and the less I can give them the better