Toss in a fourth: maintenance price. Maybe even a fifth: storage price. Funny enough, I actually have noticed this with my books. More books require more book

Toss in a fourth: maintenance price. Maybe even a fifth: storage price. Funny enough, I actually have noticed this with my books. More books require more bookshelves. More bookshelves require more real estate. It's a straight-line arrow of causation from picking up a copy of Moby Dick to house-shopping for a place large enough where I can have my own private library.