Bought a puppy from them for 180 and she had parvo...

Bought a puppy from them for 180 and she had parvo when I had got her from them she had all of her shots like the one for parvo and even fixed her so I asked why are the puppies and older dogs so expensive. She told me that they are pricy because of all the shots also because of the cost of the nudering but what I'm wondering is why spend all that money on fixing the dog and giving it shots instead of testing it for one of the most deadly and contagious diseases for dogs? So when I called them back about selling me a sick dog all they seemed to care about was getting me my cash back which is ok but when I asked so what will u do with the dog after I give it back they just said they would euthanize which seems like a bad deal for the dog so now I'm left cashing out money I don't have for a expensive dying dog that was never previously tested for parvo and I know this because the vet said on her medical records she was never tested so I will never go back to that doggy prison.