The Humble Bundle currently has a sale for all the big 2K games.
Most interesting for us are obviously Civ6, but as strategy gamers here we probably also fancy all the XCOM titles as well as Railroad Tycoon titles. This bundle also contains other titles of extremely high quality, e.g. the Bioshock collection or Mafia collection.
To get Civ6 and all the other titles you need to pay at least 15.98€.