The developers of the awesome Factorio have announced that the price is about to go up, so if you still haven't purchased it now is the time. Honestly this truly is one of the best indie games ever made, with full Native Linux support and it is Steam Deck "Playable" too.
This is the third price rise in 7 years (at least going by GBP) and it's never been on sale either, so it's not like holding out for a big sale event on various stores is going to help. The price will rise by $5 tomorrow (and likely the equivalent in your currency), January 26th, as announced by the official Twitter account:
Good day Engineers,
Next week, on Thursday 26th January 2023,
We will increase the base price of Factorio from $30 to $35.
This is an adjustment to account for the level of inflation since the Steam release in 2016.
Why don't they ever put it on sale? It's a good question and their original answer on this was about "respecting the players who have already purchased the game" and not to "reward the people who hold off on buying the game". It's a pretty fair point really and they've done well to sell so many copies without a sale with an Overwhelmingly Positive user rating on Steam.