Protein powder is sold by the kilo of powder. You are buying protein. Those are not the same unit, and the gap is wider than the shelf suggests.
Below is what a kilo of protein costs for each product: the price divided by the kilos of protein in the pack. A 1 kg bag holding 71 g of protein per 100 g contains 710 grams of protein. At €31.99 that comes to €45.06 per kilo of protein.
The number you need for that is in the nutrition table, not on the front. Protein per serving depends on a serving size the manufacturer picks.





