Depends on how you want to do it. It can be as cheap as FREE, or as expensive as however much you decide to spend on your novel.
POD makes this pretty much moot, unless you're wanting a full print run, and why would you want that?
Some people still want printed books, as opposed to e-books. A lot of websites, like Amazon, Lulu, Createspace, and Smashwords won't let you buy a book, electronic or otherwise, from them unless you sign up for an account, which some people still don't really want to do. Also, there are people who don't have regular access to the Internet, or the devices needed to download books, much less order them online. So in order to get my book out there, it seems like I have to have some physical copies on hand unless I don't mind shutting out a potential reader by telling them they're too behind the times to read my work.
Amazon includes an ISBN, and you've got copyright by virtue of having written. It's not *registered* but you have the copyrights.
Again, assuming you're okay with publishing through Amazon. Not everyone wants to do that. Nor should everyone be expected to want to do that.
This one's a legit expense, if you're not doing it yourself.
I'm sorry. I really only wanted to ask people if they did or did not use a 3D printer to make something related to their book. I don't know why I need to defend a question I've asked, or defend any potential decision I may or may not make in the future.