I kind of feel the same, but it might be due to the 3rd game being perpetually on sale on GOG, along with their age, and at this point, most who are interested have either already bought it or obtained it otherwise. If the rumored upcoming DLC comes out, that could add some more significant sales numbers.
For me, the 1st game was totally under my radar at the time of its release, while I'll never forget buying a physical copy of the special edition for the 2nd game at Target at ~$30-50 (I don't remember anymore, but I know it was up there at the time) and instantly becoming a fan.
