Sellers will charge whatever the market will bear. If all the sellers agree on a minimum price, or there is only one seller, the seller(s) can charge whatever they want.

If a particular commodity is "worth" more because it has captured the consumers' imaginations (through such means as, say, advertizing), then the seller of that commodity can pass on any increased costs due to the purchase of advertizing, and thus recoup their investment. And they do. Name brands cost more than generic brands, and it's not always -- maybe not even often -- a matter of quality.

I selected drug companies in particular to make my point because, with drugs, unlike foods, toys or what-have-you, are controlled as to their content: the proportion of "active ingredient" in the product, and the composition of the "active ingredient". Generic foods vary in taste, though their nutritional value is similar, and other products have differences in design and color, which may be construed as quality issues. (Obviously, items of inferior quality ought to cost less.) Drugs have no such quality issues. They do have R&D issues.

Maybe I should have used soft drinks. The principle is the same.