Metro Exodus was one of those major titles that was snatched up by the Epic Games Store last year just before launch of the title and was removed from the Steam Store. Unfortunately now Epic Games Store exclusivity period is about to end and the game will be brought back to Steam.
As of writing of this article piece, there is no price listing for Metro Exodus yet on Steam, but the listing does appear when you search for it on the main Store page. The DLC pricing is mentioned, but the main game price should appear closer to the time.
Metro Exodus is scheduled to launch on Steam on the 15th February 2020. So if you have not picked up this great title as of yet, I would highly recommend it, even despite the game being moved around stores, the quality of gameplay experience is something else and any fan of the Metro games will be truly happy to experience this next title in the series.