Screenwriting is a tough business. It seems like everyone in Hollywood is working a movie script, even people who have normal jobs outside the entertainment world. Walk into an LA coffee shop at any time of day or night and you'll see plenty of people hunched over Apple laptops trying their best to churn out the next Avatar or Django Unchained. Even though it is a very competitive field, every once in a while a writer gets lucky and sells their script to a studio for potential development. The majority of scripts are purchased for less than $100,000 but there have been several that earned small fortunes.

What makes a script so valuable to a studio? It could be any number of things. One is that the writer has a proven track record, as is the case with Shane Black, whose screenplay The Long Kiss Goodnight was the most expensive screenplay for quite a while. Black made his name as the writer for the Lethal Weapon series which eventually became one of the highest grossing blockbuster franchises of the 80s and 90s.

Another reason a screenplay can be worth a lot of money to a movie studio is a good "hook." This means a premise for a story that's so good that it has instant commercial appeal, even before a star actor or director is attached. The rare occasion when a screenwriter with a proven track record churns out a highly anticipated and commercially viable script can result in some seriously big bucks.

Below we have put together a gallery of the 10 most expensive scripts in Hollywood history. You'll note that while some of these screenplays went on to become highly successful movies, others weren't so lucky. In Hollywood, there's always an element of luck to financing films because you can never be 100 percent certain what audiences will go for. Still, that doesn't stop movie studios and countless screenwriters from trying to capture the next big thing. Here are the ten most expensive screenplays in Hollywood history.