R is for Return on Investment (ROI)
Put to Use
Seeing your book advertised on XYZ website is awesome, but is it worth $39 if there’s no real conversion? If their audience doesn’t click-through to buy your book, you won’t make your money back. And if you don’t make your money back, what do you get out of it? A little exposure and another Google search result attached to your name? It’s up to you to decide whether or not your investment was worth it.