There are long term health benefits to your pet when it is spayed or neutered; your veterinarian can explain these to you. Obviously, the primary benefit is controlling the pet population and reducing the numbers of unplanned and unwanted pets.
Spay and neuter procedures are a major surgery for your pet. The average spay or neuter costs less than an automobile tune-up. The procedure requires the time of a veterinarian and a technician, newly-sterilized surgical instruments, general anesthesia, drapes, suture material, and hospitalization. When measured against the cost of feeding and nurturing unwanted kittens or puppies, spaying/neutering is much more cost-effective.