Inventory management: How do you differentiate between different packaging sizes?

In the future, I would like to scan the EAN codes of my purchases to calculate and compare base prices (kg, liters, etc.). I have an item master record for each EAN code.

With beer, I have the problem that there are single bottles, packs of four, and cases of 20. All of these bottles have the same EAN code. But the respective base prices are different.

At the supermarket checkout, only one bottle is scanned, but the receipt shows the price for a single bottle, a pack of four, or a case. Where does that come from?

Is this something like with textiles, where the different sizes are sub-terms of the article?