How I Made $2...err 75 cents

While I was browsing through books today at Half Price Books, I happened upon a $1.25 copy of John Steinbeck's Cannery Row. I picked it up to take a look and was surprised to find two crisp new $1 bills tucked into the back. Perhaps it was intentionally left there to encourage someone to purchase the book? Perhaps someone was using the money as a bookmark (but then why would it be in the back of the book and why would there be $2 instead of $1)? Regardless, I walked out of the store with a copy of the book and 75 cents to spare, not too shabby.