They can afford it. You are suggesting it be deliberately priced in such a way that they can't.
I said in my opening post that it'll add on at most about £2 to a multipack of Fosters, £0.80 to a multipack of Special Brew and absolutely nothing to a bottle of Blossom Hill.
Yes, it'll increase the price of a bottle of Frosty Jacks but that's because Frosty Jacks is currently priced at about 20p per unit.