We have a pharmacy chain that does the same thing -- e.g., "Tussin" cough medicines, imitating "Robitussin", and costing only 2/3 as much as the brand name product. I discovered that the active ingredients on the label are the same, and the proportions of active ingredients are the same in the two products. If it meets that test, there's no medical difference between the two.

Yet I still buy Robitussin. Why? Because I bought Tussin once. It worked fine, if I could get the kids to take it. I could get them to take it once, voluntarily; after that, it took two of us, one to hold the limbs and the other to hold the kid's nose until he or she had to open their mouth to breathe. I remember chewing a rubber band when I was little; Tussin tastes a little like that, only with the bite of alcohol thrown in. Ew. It was easier to throw the stuff away and go back to the elixir with better flavor.

Sometimes we don't pay for the advertizing, or the medical efficacy. Sometimes we pay for ease of use.