SSD Prices Continue to Fall, Now Upgrade Your Hard Drive!
Disk Drive Prices 1955-2019 (a professor graphs the trend the cheapest price/MB since 1955, last updated 2019Aug17, I'll link the actual data table in comments) : r/DataHoarder
HDD Market History And Projections
SSD price slump shows no end in sight | TechSpot
A history of flash memory and its rise in the enterprise | TechTarget
SSD NAND prices dropping - price could further half this year