Really? I know absolutely nothing about fish and have never seen the point of a pet you can't cuddle but I'd argue that all animals deserve a good home, and that far too many are sold by breeders or shops with absolutely no concerns about the life it will have.
I cant argue with that but that would only apply (in my opinion) if i was buying a pet that would have some value if it was used for breeding, cats, dogs, chinchillas, birds & to a lesser extent reptiles.
I dont think there is any random average joe who has all the equipment let alone the patience to breed goldfish and sell them on. There is just no market for it and most unwanted goldfish either end up in other people's ponds, local rivers, poured down the gutter or flushed down the loo and end up god knows elsewhere. To get the profit margins high enough to be worth it, you'd need to be shifting hundreds of them if not thousands and thats just never going to happen.
Alternatively, I have heard of fish breeders who have an established business approaching pet shops and selling their fish to the shop but thats something else entirely.