Usually the more expensive brands, in terms of the eye shadow and stuff like that, you're paying for the pigment. Like um, the darker it is. Like, ok, for instance I'm going to put a little bit of Mac on her versus the drugstore brand and I'm going to use similar shades. Here is the drugstore brand and I'm going to put this on your forehead, I know this looks goods, versus the same color of a more expensive brand. See how it's the same color on the pallet but on her it's a lot different? It's because the expensive brand has a lot more pigment in it so you're going to have to put a lot less on and do a lot less touch ups. So eventually it's going to save you money by buying the more expensive brands. You're pretty much just paying for the heavy pigment because pigment isn't cheap.
So, the department store brands can sell it for less money but that's because they're putting a lot less color pigment in there. The only thing I haven't noticed a difference in is the quality of lip gloss. Lip gloss over the counter is the exact same as the more expensive department store brands. The only thing you're going to have to watch out for: sunscreen, I would buy the more expensive sunscreen and moisturizers, I would buy the more expensive department store moisturizers.