I am under the belief that rescues who attend these auctions go specifically to pull out the breed they are concentrating on so there will be no more future litters produced. If the dog they save is spayed or neutered and than adopted out at a much higher price because of the demand which brings in more funds to their rescue than that would make sense. However, I participated in one of these rescues where many small breed dogs were pulled and the rescue really had no money for medical bills and relied heavily on the people who were willing to foster these dogs. The small breed dog most in demand was the Yorkie, so none of those where available to me. I remember asking which ones would be the least desirable that no one would foster. One was a female manchester terrier with a hugh tumor under her belly and the other was a chinese crested but actually was the powder puff but had an extreme skin infection. Those are the two I took and after getting them straightened out, I kept them.
So there you have it. The breed that is most desirable and in demand is the one the rescue is going to try and get the most money for. I have seen it first hand with a whole circuit of rescue groups accross the country. My only interest was to help but did I get an eye opener.