I've heard some horror stories from people who have bought pets from breeders. One was just on The People's Court recently for selling a dog that was obviously sick in advance of the purchase. Needless to say, the dog passed away shortly afterwards and the owner was out of a dog and a lot of money.
I think the term "mutt" is unfair and misleading too. A "labradoodle" is a "mutt" generally speaking, but now breeders are charging top dollar for them. There are many unique and gorgeous "mutts" at the pound, that also have the added benefit of not having so many health problems from all the inbreeding. I had an incredible coonhound mix for 15 years that I wouldn't have ever traded for any purebred in the world.