I wonder if that's tracked to inflation. A $400 medical expense from 2013 is likely closer to $500 today, which might account for the difference from 50% to 40%.
All of these are commodities. And every single product derived is based on commodity. Most commodities can be traded on commodity markets.
https://www.bls.gov/charts/consumer-price-index/consumer-pri...
1: https://www.statista.com/statistics/184955/us-national-healt...
Source: https://www.thebalance.com/causes-of-rising-healthcare-costs...