Breaking news: books not written with movie budgets in mind
According to The Numbers and Galleycat, it seems that turning a book into a movie is crazy expensive. From the list of the top ten most expensive movies ever made, seven of them were adapted from a book or comic book. This doesn't shock me; books aren't generally written with a movie budget in mind, and can delve into some pretty fantastical places. While a writer trying to pitch a movie script will have to be mindful of the limitations of their chosen medium, a novelist isn't restrained by how difficult and time-consuming it would be to make a pirate ship fly or to have a dragon light the forest on fire or to fill a vault with shiny shiny gold. They don't have to worry about props or special effects, so they can write whatever they feel like, so long as it sound cool. And then some years later, Hollywood gets ahold of it and says "hey, this would make a fantastical movie..." Which means they then proceed to either bring it to life or destroy it, but that's a topic for another day.