[riffraff]

it is an EU thing [0][1]

   Easy comparison – price per unit
   You should also be able to compare prices between brands and between package sizes – to see, for example, what saving you'd make buying a large-size box of breakfast cereal instead of a small box.
   To help you do this, all products must be marked not only with the selling price, but also the price per unit – for example, the price per kilo or per litre. This information must be understandable, easy to read, and easily identifiable.
   This rule also applies to adverts that mention a selling price.

Notice this does not apply uniformly since it delegates to national regulations, so e.g. IIRC in Italy supermarkets list the number of "bits" you can rip off a toilet paper roll, but in Hungary they don't.

^0 https://commission.europa.eu/law/law-topic/consumer-protecti...

^1 https://europa.eu/youreurope/citizens/consumers/unfair-treat...

[kranke155]

Its a beautifully simple measure that helps me every day.

[g-b-r]

Yes it's crazy how much it helps, I always look at them now when choosing among products

I almost feel sorry for the producers