In a recent interview with Philippe Morin, one of the founders of the studio Red Barrels and the chief developer of games talked about the game and announced that, despite the many differences around it has managed to sell close to one million copies so far.
According to Steamspy data, the game was able to sell 200 thousand copies on the PC and the rest of this version was sold on the other platforms, which gives us an impression of the size of the PC market at least for the Outlast 2, which is much lower than its predecessor and to this day to sell 2 million Copy almost.