I have recently started doing this too - I prefer r/iTunesMovieDeals for discovering stuff on sale. What I have been trying to optimize for is a low cost per hour and a high critical rating.

For example, I recently got the entire bundle for HBO's Rome for $9.99. That is ~50 minutes per episode (22 episodes), or $0.54/hour, which is not a bad deal! For a casual viewer like me, who might spend <6 hours each week watching TV, this should last a little more than 3 weeks. Recently, The Sopranos went on sale for $29.99, or $0.38/hour.

For streaming vs. buying to work, you just have to be patient about nabbing ~1-2 purchases per month and not be tempted to buy every single day.

The best part is the reduced cognitive load - you don't have to spend time browsing for content every day, and there are no ads, too.