From a practical standpoint, that’s probably an even bigger money-loser than the traditional method of making money as a breeder. From what I’ve heard, most ethical breeders who are really interested in improving the breed barely break even.
There has been speculation that cloning purebred pets could lead to a loss of genetic diversity, which could cause problems for the breed similar to those caused by excessive inbreeding.
It seems like a ridiculous waste of money, but I don’t see why it would be unethical or ethically favorable.
If one believes (and I don’t) that spending money on anything non-essential is unethical, then that might support the argument that it’s unethical.
From a breeder’s standpoint, it seems like a very complicated, expensive way to create quality stock, and I think it would only serve to pull down the price of quality stock. So it probably has little practical appeal to the professional breeder. Speaking from experience with horse breeders, there’s not a lot of profit margin on an animal, even on a quality animal (a handful of racehorses notwithstanding - much of the animal’s sale price represents the sheer cost of raising and training it to get it ready for sale). For the vast majority of breeders, then, it’s probably not an attractive option.