How does Audible Whispersync deal pricing work?

When you own a Kindle ebook, Amazon/Audible often offers the matching audiobook at a steep discount — sometimes $1.99 to $7.99 — via Whispersync for Voice. This "Add Audible narration" deal lets you own the audiobook at a fraction of normal cost. You can find these deals on any Kindle book product page on Amazon that has a matching audiobook version.