If you buy Rainbow Six Siege on Uplay right now you get a $24 credit basically making it free.
*If you purchase Rainbow Six Siege "Standard", "Year 2 Gold edition" or "Complete Edition", you will receive $24 in store credit for your next purchase. Store credit will be in the form of a promo code that will be sent via email on September 7th. The store credit can be used on any game (excluding pre purchase games) sold on the Ubisoft store during a 7 days period from the date of receipt of the email, ending on Sept 14th at 11:59pm PST. It is a one-time use only code and no balance of unspent credit can be used on future purchases.