Personally, I buy protein powder even though I know the ingredients are actually too cheap to justify the price. But I’m too lazy, and the reward of a cold chocolate shake after working out makes me forget about the outrageous cost. It’s a little guilty pleasure I’ve come to terms with.
I pay 42€ for 1kg. I don’t know what makes it so expencive or why your’s so cheap. Maybe because mine is vegan. I don’t know.
But Soy is quite cheap. 100g of Soy granular costs about 1,90€ and has 52g of proteins.