Whenever you are out shopping for things is it cheaper to buy the product from a store that specializes in the product or a store that is wholesale and has your product in it?

For example,

Buying o.t.c medicine- Cheaper to buy at a pharmacy or walmart?

Buying food- Cheaper at a food store or a place like walmart again?

Buying shampoo- Cheaper at a hair store or a food store or a walmart?

Do you get it? I dont want to know that Head & Shoulders is cheapest at your local gas station, i just mean in general.