How did you come to this conclusion? Even buying several products from the Ordinary to layer (if one is so inclined) is going to be cheaper than one serum from a premium brand in most cases. Advanced Night Repair is €95 for 50ml, if someone used two serums from the Ordinary (let's say hyaluronic acid and the buffet serum, based on ingredients), that's still only going to come to about €25. You'd have to be seriously layering on multiple products for it to not be cheaperALSO buying single ingredient skincare isn’t cheaper. It just means you’re more in control of the eventual formula. But you still need a few things to layer or mix.