Pricing for convenience

I visited my local Co-Op yesterday evening and was struck by the pricing being used here. I noticed it because I hadn’t seen the 1/5 litre oat drink before so it caught my eye. But then I saw the prices and it made me wonder how much convenience is worth . Buying the small carton could be seen by some as better environmentally because if they only use a small amount there is less waste for a product with a short life once opened. Or sometimes for a range of reasons carrying a smaller container can have benefits. But if the choice is there between these two and the price is identical it is surely hard to justify buying the smaller carton.

I have seen similar with bottled water where 2 litres can cost the same as a half litre, and a 1 litre bottle more expensive than either. That definitely works to the convenience level of a bottle of water to drink there and then. But I’m not sure how much that applies to oat milk. What does anyone think?