Amazon can't actually sell the book right now. Nobody online can. I think the inflated price is just there to keep people from trying to buy it. The Permuted Press edition is out of print, and another publisher is going to be taking over soon.
If you check JohnDiesAtTheEnd.com, there's an announcement of an unspecified further announcement to be announced on Tuesday, which is when the story (which has been available for free on the website up until now) gets taken down. Then, whatever it is that's being announced will come out at midnight on Halloween. Smart money's on that either being the new edition, or the final chapters of the sequel, or an alternate version of the novel told from John Cheese's point of view, or some kind of news about the movie, or maybe some combination of those.