The harm done in the US by mismarketing of drugs is around $27 billion dollars a year, which is comparable to the amount that Big Pharma spends on research.

Patents encourage mismarketing just as they encourage research spending, so it could be that patents do so much harm through mismarketing alone that it outweighs their incentivization of research. But the raw numbers exaggerate the benefit of Big Pharma's research, since it focuses research on developing the next viagra rather than on curing dangerous diseases.