Amazon offers Prime members the Greenies Canine Dental Chews 27-oz. Bag for Petite dogs for $15.90 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $7.53.) That's the lowest total price we could find by $6.45.
Of note: It's available for Large dogs for $16.91 with free shipping.