Yeah I don't know, I don't use shampoo or soap in the shower, and haven't really in over a year (rare exception is when I get car oil/grease on me.) Only cosmetics I buy are Barbasol shaving cream (the cheapest brand here) because Barbasol actually works better for me than the expensive fancy Gillette shaving gel stuff that costs like 3x more, and a bottle of Adidas aftershave every few months. I used to buy knockoff colognes that smelled exactly like the real thing, but unfortunately now I have to get those online, but my convenience store sold them cheap. Oh, for razor blades, too, I have a double edged razor, so now fancy cartridges that cost like $10-20, though the Personna DE blades are kinda expensive around here.
Good luck with the cosmetics thing, though, but yeah, I don't use most of them. Since I stopped using soap in the shower, my back acne is gone, same with dandruff. I do however, occasionally use vinegar/lemon juice in my hair, actually as conditioner, as the acidity will make your hair's "scales" go down. The reason why just using bar soap will make your hair all sticky and bad is because it's alkaline, so acid does the opposite and makes it silky smooth.
Yay cosmetics.