It turns out that that Stephen King quote in the first Alan Wake was a gift from the author himself, and it only cost Remedy $1.
You don't need to be a detective to see the Stephen King influences on the original Alan Wake, even ignoring the fact that the titular Alan quotes him right at the start of the game. But in an interview with Eurogamer, Remedy boss Sam Lake spoke of how important it was to him to get a quote from King himself into the game. "Creating the original Alan Wake, I really, really desperately wanted a quote from him to start it off," Lake told Eurogamer. "It's my understanding he wanted $1 for us to get the rights to use it. [It was] so very generous."
A single dollar is obviously quite the bargain when it comes to intellectual property rights, and feels pretty on brand for the general ethos that King seems to exhibit. It's quite the way to start the game, and likely wouldn't be as good an opening without it.