The only safe thing to inject into your buttocks is your own fat and this procedures is called a Brazilian Butt Lift, BBL. The costs of BBL varies based on location of the practice, the physician, the patient's anatomy, and the number of areas that are needed for liposuction in order to harvest the fat to be injected into the buttocks. I wouldn't choose a surgeon on cost alone, but look at their results and choose one you feel comfortable with. Additionally, most plastic surgery practices offer payment plans through financing companies such as Care Credit and Alpheon. I recommend consulting several surgeons to help find the one that is right for you. Good luck! Kamran Azad MD, Board Certified Plastic Surgeon