Small to medium-sized dogs. 1  Estimated life span: 14 years. 2  First year: $740 to $1,325. 3  Estimated annual costs thereafter: $500 to $875. Total cost over a dog's lifetime is about $7,240 to $12,700.  Estimated life span: 8 1  years. First year: $1020 to $1,825.  Estimated annual costs thereafter: $690 to $875.