In recent months, Amazon CEO Jeff Bezos has insisted that the company focus on securing a hit show on par with HBO’s Game of Thrones. With this Lord of the Rings deal, he secures the rights to an even more popular epic fantasy—just as HBO’s juggernaut is set to end its run.

The upfront costs of $200 million to $250 million seem staggering. Those figures don’t include a production budget, which could be more than $150 million per season, or tens of millions of dollars in potential marketing costs. All told, Amazon could wind up paying half a billion dollars before anybody sees one minute of content. According to Deadline, industry sources have called the deal “insane,” given the size of the up-front commitment and the fact that there are already six installment (and 15 hours) of Peter Jackson’s trilogies of The Hobbit and The Lord of the Rings.

But perhaps it’s precisely the existence and proven success of those films that justifies Amazon’s extraordinary deal. Jackson’s six Middle-earth films have a combined global box office of about $6 billion. Game of Thrones, its thematic descendant despite being adapted from the books by another author, George R. R. Martin, is the biggest hit in HBO history.

One might think that six Tolkien films and seven Game of Thrones seasons is fantasy overkill. But the single most important media-industry lesson of the 21st century might be this: Overkill is underrated. Consider Disney’s endless Marvel franchise, which is now on its 17th(!) film. The franchise has earned $13.3 billion for the company and shows few signs of slowing down, relative to the competition. Two of the franchise’s most recent installments, Guardians of the Galaxy Vol. 2 and Thor: Ragnarok, are respectively the second and fourth biggest opening weekends of 2017.

There are several takeaways here. The most fundamental is that in a crowded media environment, audiences reliably gravitate to stories that they know, not hours of content with no recognizable hook, which might turn out to be a total waste of time. Indeed, despite the fact that Netflix, Amazon, and Hulu are spending billions of dollars a year on original shows, 80 percent of the viewing time on subscription video sites is spent watching “back catalog” content, including reruns and movies that have left theaters.

Due to this preference for familiar storytelling, it’s difficult for media companies to use a “Moneyball” strategy for entertainment content. Moneyball, for the uninitiated, refers to a strategy of using advanced analytics to spot underappreciated talent. In a sport like baseball, it often works by identifying middling players who are secret stars, whose star-making skills are unfamiliar to most scouts. But in media, where unfamiliarity itself is the enemy, the most valuable franchises—or, in industry speak, “intellectual properties”—are often, almost by definition, those that are already well-known to audiences.