I'm surprised that people think dogs are the most expensive, although I'm pretty sure the reasoning stems from the fact that dogs are usually the easiest to "spoil".

I myself voted for dogs before I remembered how much exotic birds cost.

On average:

Hyacinth macaw - $10,000 !!
Greenwinged macaw - $1500-2000
Blue and Gold macaw - $900-1200
Umbrella cockatoo - $1000-15000
Sulfur-Crested cockatoo (Lesser and Greater)- $1000-2500
Moluccan cockatoo - $1800-2500

Let's not forget DNA sexing and avian veterinarians are difficult to find so vet bills are naturally pricier.