> labels including the "price per unit weight/volume"
We overestimate the average person.
Not everybody knows what that even means. They just don't have a concept of ratios that can be compared.
> go for the cheaper product price.
That might still be a valid option if the packaged quantities differ my a lot. E.g. if I only need 100g of ham for a sandwich, it's not better to buy a whole 1kg piece if that's just going to rot in my fridge.
I don't think we overestimate people necessarily, I think we overestimate how much they desire to spend their time thinking about the same things we do.
We overestimate the average person. Not everybody knows what that even means. They just don't have a concept of ratios that can be compared.
> go for the cheaper product price.
That might still be a valid option if the packaged quantities differ my a lot. E.g. if I only need 100g of ham for a sandwich, it's not better to buy a whole 1kg piece if that's just going to rot in my fridge.