Generic drugs contain exactly the same active ingredients as

The OA is B. Here is the OE:

the conclusion of the argument has two parts: (1) that generic drugs are just as effective as their brand-name counterparts and (2) that generic drugs cost less than their brand-name counterparts.

The Correct Answer is B. The effectiveness of a drug depends not only on its having certain active ingredients but also on the drug being correctly manufactured so that it has the right composition. (B) tells us that generic drugs are no more likely to be defective in their composition than brand-name drugs are, thereby strengthening the arguement for part (1) of the conclusion.

The OE eliminates (A) on the following basis: We already know that generic drugs contain the same active ingredients as their brand-name counterparts. So the fact that the ingredients used in the manufacture of brand-name drugs are no more expensive than those used in the manufacture of generic drugs provides no additional evidence concerning the effectiveness of the generic drug. And A clearly does not add support for the conclusion that generic drugs cost less than their brand-name counterparts.

My follow Up Questions:
I think AC "A" does provide support for the conclusion that generic drugs cost less than their brand-name. Here is why:
Total Cost of Drugs = Cost of production of drug [ingredientcost+development cost+marketing] + MarkUp.

But based on the premise [generic drugs contain exactly the same active ingredient as their brand-name counterparts, but cost much less to develop, produce and market] we now know the "cost of production" is the same. This premise in conjuction with the above equation proves that its the "markup" of brand name drugs that is hiking up the price. Therefore it supports the conclusion that generic drugs cost less.

What is wrong with this logic? How could the author say that AC A doesnt add support to the conclusion that it is generic drugs cost less than brand-name drugs.