Separate the first year from the ongoing year
The first year includes vaccination, neutering or spaying, microchipping, a carrier, bedding and a first vet check. Those are not annual costs and should not be averaged into a monthly food budget.
From the second year, food, litter, routine checks, grooming and insurance are the recurring lines.
Food and litter scale with the animal
A large dog eats more than a cat, and a prescription diet can cost more than a supermarket brand. Compare the cost per day or per month for the actual product, not the shelf price per bag.
Vet care is the volatile line
Routine care is predictable; an emergency is not. Pet insurance converts a large unpredictable bill into a premium, but it has an excess and exclusions. An emergency fund is the alternative, not a reason to skip either.
Boarding, grooming and travel are easy to forget
Holiday boarding, grooming, pet-sitting and travel documents are real annual costs. Ask the boarding facility for its vaccination and cancellation rules before you need it.
Heat and travel matter in the Gulf
Outdoor exercise in extreme heat, air-conditioned space and travel paperwork can change the cost of ownership. A pet that cannot travel with you needs a boarding plan.