Total medical R&D spending in the US is a few hundred dollars per year per person, out of about $10,000 in total health care costs. That’s everything, not just private drug research. Research does not explain the huge discrepancy in costs.
For the big pharmaceutical companies, about 20% of revenues are spent on R&D. So you just paid $1000 out of pocket for a drug? About $200 of that is funneled back into R&D.