Tesco are past masters at these reverse offers! I have complained to them many times when it is cheaper to buy two single items than two on offer. The problem comes when you buy two, but do not want the "offer" to be applied. I just tell the cashier that they are two single items and please do not apply the offer!! Otherwise one will get left at the checkout!!
Oh grow up some of you. Food prices are creeping up and up. If you're canny/lucky, you'll find a box/bag/packet of something that though twice the size, is the same price or even cheaper, than a smaller version of the same. Occasionally mistakes happen, but only an idiot would think that supermarkets deliberately mis-price goods,
and he tells me that many of their stores carry over 40,000 individual product lines. It's not difficult to understand that occasionally there will be pricing errors, and to suggest that there's a deliberate policy of mis-pricing "for some obscure reason" is just plain foolish.