It’s more expensive than the ebook ($14.99 vs. $3.99). We’re not deliberately engaging in price gouging; this is near the minimum price CreateSpace will let us charge.
The content of the physical book is exactly the same, links have been replaced by endnotes, and graphs are in color. It’s an ideal complement to the ebook, and it also stands on its own. Especially when ordered in huge quantities… 😉