The "Founder's edition" pre-order bundle for Google's Stadia includes a Chromecast Ultra along with the controller and costs $130. Now you can get just the controller on its own in one of three colors. You may still want to get the full bundle even you already have the Chromecast, though. The controller alone is $70, so you're saving $60 - that's how much the Chromecast Ultra costs. However, the bundle comes with 3 months of Stadia Pro (normally $10 a month) and a Buddy Pass to invite a friend. The free tier of Stadia will not be available until 2020, so you can't use that to test the...
Source: https://www.gsmarena.com/standalone_controllers_for_google_stadia_now_available_for_preorder-news-37636.php