Both the Ryzen 2600 and 3600 were priced at $199 upon release. See the "Price at introduction" in the following links.
Ryzen 2600: http://www.cpu-world.com/CPUs/Zen/AMD-Ryzen 5 2600.html
Ryzen 3600: http://www.cpu-world.com/CPUs/Zen/AMD-Ryzen 5 3600.html
The reason the Ryzen 2600 is so much cheaper now is because of the dumping of old inventory and holiday sales.
I was able to recently buy a new Ryzen 2700X processor with Wraith Prism fan/heatsink for $129 + tax during the Black Friday/Cyber Monday sale time frame. Originally this sold for $329.
Ryzen 2700X: http://www.cpu-world.com/CPUs/Zen/AMD-Ryzen 7 2700X.html
And in my case, Indonésia continuous dive of currency exchange rate also helps to increase the price gap.