Via Time.com:

It’s no secret that Steven Spielberg and George Lucas are good pals, but perhaps the best demonstration of their friendship is the fact that not even a $40 million bet has been able to come between them.

Back in the late 1970s, Lucas was reportedly nervous that his upcoming sci-fi film Star Wars wouldn’t be a big hit. At the time, Spielberg was in the midst of making his own sci-fi epic, Close Encounters of the Third Kind. With Jaws already under his belt, Spielberg was the better-established director. During a break from filming on Star Wars, Lucas visited to the Close Encounters set. According to an interview with Spielberg for Turner Classic Movies, the visit did little to allay Lucas’ concerns:

“He said, ‘Oh my God, your movie is going to be so much more successful than Star Wars! This is gonna be the biggest hit of all time. I can’t believe this set. I can’t believe what you’re getting, and oh my goodness.’ He said, ‘All right, I’ll tell you what. I’ll trade some points with you. You want to trade some points? I’ll give you 2.5% of Star Wars if you give me 2.5% of Close Encounters.’ So I said, ‘Sure, I’ll gamble with that. Great.’”

Lucas was right that Close Encounters would be a hit, but it was Star Wars that would become the standard-bearer for the genre. The film made $775 million at the global box office compared with $304 million for Close Encounters. Adjusted for inflation, Spielberg’s edge could come out to as much as $40 million.