This makes sense in the same way it makes sense in every other industry. They need to recover all of their sunk costs within a few years and marketing greatly increases rate of uptake and overall sales. Marketing frequently provides a positive return on investment, and in cases where the window to make a profit is short it is essential.
It would be silly to invest marketing dollars in R&D if none of the developed products were able to return the cost of R&D within the patent window due to slow market uptake. The idea that these are independent or that marketing is a waste of money relative to R&D is pernicious and incorrect.
It may apply in other industries, but medicines are different. You have the whole medical school system to do your "marketing". There are scientific publications galore.
For life-saving drugs, customers aren't swayed by "marketing" at all: if they have a condition that can be helped by the drug, they will go for it, marketing be damned.
I know we like to jump to analogies in these forums ("digital music" == physical stuff; "no password" == unlocked door; etc.), but some situations are unique. I would like to think that the pharma industry, particularly the critical drugs section, is unique.
The medical school system and journals is too slow for a new drug. By the time new doctors have enough influence, the drug is out of patent, and you can't count on every doctor to follow up journal articles about every new drug.
(I also recall hearing that advertising costs are stuffed into the inflated R&D claims, but it's hard to really know how much, due to lack of transparency.)
