@turkay1-- Yea, commercial dandruff shampoos labeled as "natural" cost more than regular shampoos. But if you don't want to use them, you can make a natural shampoo for dandruff at home. Now, it won't be the same because you won't get as much lather (or any lather) with homemade shampoo. But it's definitely much better for your scalp.
My favorite homemade dandruff shampoo recipe is made by boiling mint leaves (fresh or dry) in water and taking that water. Next, you can add either coconut oil or all-natural soap to it depending on how oily your hair is. If you have dry hair, add coconut or olive oil. If you have oily hair, grate some natural soap and add that in.
This is such a simple recipe but it works really well and costs very little.