[billybob]

"Denzel Washington and Leonardo DiCaprio are fine actors, but you don't need an actor of their caliber or pay to make a decent movie."

Paying millions for DiCaprio isn't necessarily because of acting talent at this point. It's because of name recognition. If you think that $X in actor salary will get you $5X in box office net, you'll pay it.

From the moviegoer's standpoint, if you have seen movies with DiCaprio that you liked, you'll be more likely to see another movie with DiCaprio. Ergo, the "big name" strategy pays and continues to be used.