The U.S. Bureau of Labor Statistics data shows the rise and fall of drug prices from 1969 to 2019 and the drop was not for the first time in 2019.
According to the data published by the U.S. Bureau of Labor Statistics,
the fluctuation of the average price of prescription drugs in the country can be observed between the span of fifty years (1969 to 2019) (To access the data select the 'From' and 'To' dates from the drop-down next to 'Change Output Options' and select the GO button.)
The price drop at the end of 2018-2019 was -0.4 (March 2019). The same column shows that there has been such price drop multiple times over the 50-year-span and not just for the first time in 2018-2019.