Mandibular plastic surgery includes many items, such as mandible resection and grinding, and whole face modification.
If you mean simply short chin, I suggest that you can use chin pad. Implantable prostheses can generally use silicone, swelling and other materials.
Prices vary according to different regions and doctors, generally ranging from several thousand to one or twenty thousand. Please don't simply consider the price factor, the effect is the most important!