I have a 5yr old heeler of my own and here are a couple of things I can add to the conversation to keep cost down and a happy dog:

1. Go with an no grain food - tends to cost a little bit more but will get rid of all the "fillers" that usually come in cheaper food. Your dog will eat less due to the higher protein levels, have a better coat, and stools will be smaller as they actually digest and use the energy in the food. My heeler weighs around 35lbs and eats a little over 1/2 cup twice a day. It might be a little more expensive to buy the food, but will help further down the road and you will most likely get healthier years out of them. ~$65 every month and a half

2. Don't feed from the table. Again, this will cause a weight issue which tends to lead into higher cost vet visits down the road. A lot of heelers tend to get the sausage look because of over feeding and will put a lot of strain on their hips.

3. Check on your dog after trips - a lot of insects, cuts, stickers in their paws can be removed before they become a problem

4. Exercise - especially with a heeler. If you run them hard on the pavement look into a supplement for joints. Cheap preventative maintenance goes a long way to keeping your dog healthier longer as heelers tend to live around 12-15 years. One even lived into its 30's I believe.

Shots - I get the normal ones every year ~$200
Annual check up - I tend to go without this if the dog looks healthy. Vet only takes temp, moves the joints around a little bit and is usually pretty useless for the $75-100 they charge
Kennel - go craigslist as they are everywhere
Flying - this has gone up a lot recently as most airlines don't fly pets anymore. I have to fly mine cargo sometimes and is around ~$200-300 depending on the airline (one way). You also have to get a health certificate for 10 days prior to the flight which costs about $75. Boarding can be cheaper.
Extras - ~$100 (toys, collar, leash)

I've found that after the puppy phase, dogs are pretty cheap as long as you keep them healthy through diet and exercise. If you find your dog prone to injury, get a pet policy ($400/yr) that will take care of all shots, vet visits and even some bigger issues that might come up. Can potentially save you a lot of money.

Total for me is around $800-1000 a year but is worth it as I am more active and tend to stay in and eat instead of going out (money saved)