Google is currently running a promotion where-in the company is offering Play Store users 75% off the store price of any one movie rental. It's a limited time offer that ends January 4.
Keep in mind that the promotion is only available in select countries, including the US, UK, Australia, India, France, Russia, Italy, and Japan. Also, it's worth stressing that the discount - which gets applied at checkout - is only valid for a single movie rental per user.
Aside from this offer, Google is also running many other promotions (head to the Via link below) for Play Store users. For example, it's offering 3 months of Play Music subscription for just $1, although the deal is only valid for new subscribers.