Google is celebrating fourth of July by offering four months of free subscription for Google Play Music and YouTube Red subscribers. The two services normally cost $9.99 per month combined (you get one with the other), which means you are getting a good $40 worth of discount. The offer is only available to new subscribers, however, and not for existing ones. Also, it's limited to the US for now. Source
Source: http://www.gsmarena.com/new_google_play_and_youtube_red_subscribers_get_first_four_months_free-news-19179.php