Not just the purchase price of the dog, but the many years of expenses that come with any dog, i.e. food, routine veterinary care, and emergencies that always seem to happen at the worst possible time?
If you are already "stressed" by your daily schedule, how are you going to care for your "four-footed" friend?
When bringing a puppy or adult into your family, we must never forget that the puppy (or adult) was invited there by you and that you are responsible for seeing that he/she is taken care of properly.