As the title says, Old World, as well as addons are currently 50% off. The main game costs 19.99, the whole bundle with addons for 47.19.
This currently seems to be only the case in the Steam store, https://store.steampowered.com/app/597180/Old_World , but we are waiting for confirmation by the developers if this will also apply to GOG and the Epic store. Please check for updates in this thread.