A dog, is a dog, is a dog. A poorly bred Yorkie isn't much better than a mutt, IMO. To a person that only wants a pet, doesn't want to breed or show, there isn't much difference.
It only makes sense to spend really
serious money for a show quality dog...forget paying large money to a backyard breeder who has no idea of the genetic lineage of their litter. I don't understand why so many people are continuing to do this. It's wrecking the breed. No wonder Yorkies are ever more prone to genetic disease. It seems to happen to any breed that becomes popular.