My vet (Okay, actually my dog's vet, I see a proper M.D.) back in the 'States is adamant about feeding your dog quality food. The cost of the premium food will come back to you several times in savings as your pooch will have fewer health issues (i.e. visits to the vet).
Dogs are no different than people: quality food + exercise + regular medical care = higher quality and longer life.
And as donkey says, your dog will be a best friend for life. If I add up every penny I've spent on my dog, it's still easily less than say two family vacations. And he brings me so much more happiness than a 2 week holiday. In fact, you could easily make a case a dog is one of the least expensive things in life in terms of producing health and happiness. People with dogs are also on average, healthier, live longer. etc. Man's Best Friend: Physical, Emotional, and Social Benefits of Dogs
Okay, the cost of owning a 55 lbs dog (basics):
-Food. 30 lbs bag of premium food costs $560. Lasts about six weeks. $100/week.
-Treats. Huge range of prices and types but I would figure $50/week. This is not frivolous. They need rewards while training and to reinforce good behavior - again, no different than people.
-Toys. My dog is an adult so don't need as many as for puppies/younger dogs. About one toy/month @ $80/toy
- Basic grooming. I bathe him myself. He has fur (like Ger Shepherds, Huskies, etc) rather than hair (poodles, golden retrievers, etc.) so he doesn't ever need a trim, just brushing. Bottle of shampoo will last me a year. Cost $100 (guessing for HK). I clip nails myself. Nail clippers @$100 (guessing for HK). Other home grooming expenses will be hair brushes, toothpaste/tooth brush (oh yes, they need dental care too), towels, etc.)
-Annual vet visit. No idea what this costs in HK.
-Basic training course(s). No idea what this costs in HK but DO NOT skip this. Some rescues in the San Francisco Bay Area (were I'm from) will not allow you to adopt a dog unless you sign a contract that includes a stipulation you will enroll/complete basic obedience training w/your dog.
-Meds. Monthly flea/tick prevention meds. Monthly heart worm preventative meds.
-Boarding/Sitter/Walker. If you work long hours. When you go on holiday.