What the author didn't (and couldn't) include in their calculations is how many of those that bought the fourth book were hooked in the series BECAUSE they pirated the book(s).

How many sales would she have had if there were absolutely no copies available online for free for any of the books?

I admit, I pirated when I was young because I didn't have any money and many books weren't available in my country (or would only become available after some years). Now that I have money and I'm into reading, I spend a lot more on books than I would have if reading wasn't available to me.