I honestly don't think that a responsible, honest, reputable breeder looks into 'profit margins'
I don't see why not, it would be quite reasonable to do so. It applies to every other area of business. My husband is self-employed, and you *have* to consider profit margins, it's what businesses do. I am not criticising breeders who charge more - if they can get the price, good for them! Just because it involves live "goods", doesn't mean that a business wouldn't have the same considerations as one, say, selling cars, sheds, furniture, etc.
It is also sometimes which area of the country the puppies are, that can have a price difference. Ime the cost of the puppy is often 'guided' by the breed club. If i had never bred a litter i would think £800 is extortiante, but knowing what i know now, it really isn't.
I don't think it's extortionate, I just think it's more than I need to pay for a well-bred puppy from a reputable breeder. So far I've checked with three reputable breeders, the sort where you reserve a pup before it's born, that have both the sire and dam, that don't advertise, all within the same area of the country - the prices quoted were £600, £650 and £800.