Shelter dogs vs. Breeder dogs

I live in Australia and have had 1 purebred and 1 shelter dog. The purebred was only slightly more expensive than the shelter dog but was a necessity because my sister is badly allergic to animal hairs so he had non-allergenic fur. To adopt dogs from shelters in Australia, you generally have to pay around $200 not including any donations to the charities that keep them. Most people want puppies and/or purebreds, and when it costs virtually the same to get one of those as it does to adopt a pet from a shelter, I don't think people really consider the difference they'd be making to that dogs life. On the question in point lol, I think there are laws here preventing overbreeding or excessive breeding of purebred dogs, but as with everything people break the laws and wnen there are 'more serious' things going on, I don't think it's really policed.