This thread caused me to look up why they don't do sales. I was a bit frustrated at first; but I must say, after reading their rationale, that now I'm kinda convinced.

To quote one of the Factorio mods/staff:

> It isn't about visibility or sales, its about respecting the players who have already purchased the game. We don't want to reward the people who hold off on buying the game, the game is a price we find reasonable, and this is the deal. If you think it is priced too high, then it is your choice to not purchase, and we hope that with enough time, and extra development, we will be able to convince you of its value.

Sources:

https://forums.factorio.com/viewtopic.php?p=159626#p159626

https://www.factorio.com/blog/post/fff-140

https://www.reddit.com/r/factorio/comments/8stbnl/psa_factor...