Not that expensive considering Valve doesn't make crap hardware and has decent support. Just look at some of the reviews for the most extensive Xbox controller and how many develop drift within months. Plus the touchpads.
After reports that Valve had received shipments of the accessory, a Steam Controller review has appeared. Deleted ahead of a likely release date update, a YouTuber praised its responsive dual trackpads. Even so, the price may make it more difficult to discount the Steam Machine.