The answer is provided in a recent white paper by Pearson, Schapiro and Pearson (2022). They use IQVIA data through 2020 across 389 drugs treating 1.8 million individuals. The study finds that while 5% of drugs with an orphan indication cost more than $500,000 per year, these drugs make up only 0.08% of all patients treated by drugs with an orphan indication. The majority (52%) of patients who receive treatment an orphan drug get the treatment for <$50,000.
