They&#x27;re like software: really cheap at the margin to make the 100,000th copy, really expensive to make the first one.  Textbooks are pricey and Harry Potter is not because textbooks sell hundreds of copies and Harry Potter sells hundreds of millions.  (With a wee bit of portfolio theory going on where HP also has to pay for advance checks written to all the talented single mothers on welfare who write books in obscurity but who are not J.K. Rowling and do not become billionaires because their books have more typical outcomes and sell ~X00 copies worldwide.)