What do you don't know about some of the animal welfare groups is that when a dog is heartworm positive they will treat the dog before placing it in a home. That costs way above the $150.00 fee that is charged. Also some of the dogs need special things done before being placed in a home. SMAWL doesn't make make money on the adoptions. The vet fees for a heartworm positive dog alone are(from this vet): $500 for a medium sized dog and $600 for a large dog.
Link here for cost
Also remember that SMAWL took in many hurricane katrina dogs, and placed them in homes. Many of those dogs had health problems, that needed to be resolved before being placed in a home. They also don't have enough foster homes, and board the dogs that are not in foster homes at local kennels.
The dogs that leave SMAWL are now micro-chipped, and are spayed & neutered if it has not been done yet.