R&D investment
If you're talking about money spent by the companies themselves, that's supposed to be built into the price structure of the drug, and recouped through sales. Thus the cost would be accounted-for by looking at expenditures for pharmaceuticals.
Other nations just get to buy the drug off the shelf.
It seems to be the case that prices are higher in America than elsewhere; there's a good reason for the cross-border pharmaceutical trade with Canada and Mexico. I've never heard a satisfactory explanation for it, and it may well be, as you imply, that Americans are subsidizing more than our fair share of development cost for pharmaceuticals. It could just be that we have the deepest pockets to pick--charging what the market will bear. I don't know of anything going on more sinister than routine greed.