Radiesse is a cosmetic filler that is typically priced per syringe, and can vary based on geographical location, experience of the injector, the correction desired, etc... I would recommend consulting a Plastic Surgeon, or Cosmetic Dermatologist in your local area.
It depends on how much is needed. I usually use 1/2 to a full syringe for chin augmentation. This cost can be $500 - $800 and up depending upon the amount used. You may also consider additional syringes to build up the jaw line to enhance the effect.