I was hunting for a deal on the 'The Expectant Father' audiobook myself a few months ago. A lot of people automatically go straight to Audible, and yeah, using a credit gets it for you, but if you're looking to pay less, I'd recommend checking Libby or Hoopla first if you have a library card. It's free, though you might have to wait.
What worked for me was actually Google Play Books. They had a promo that wasn't really advertised, just a lower price than the others for a weekend. Kindle Unlimited sometimes bundles audiobooks with their subscription too, but that's hit or miss. It's worth setting a price alert on sites like Chirp if you're not in a hurry.