Please don't forget also that there is a larger purpose behind the keeping of rare and minority/traditional breeds, which is ultimately to the benefit of those who rear sheep as their livelihood. This is the preservation of traditional breeds through times, such as now, when they are not popular commercially. You may say that they are rare for a reason, implying there is something wrong with these breeds, but they are simply out of fashion or, more likely currently inappropriate for today's needs. The reason they need to be preserved is so that when conditions change, as they are doing all the time - climate, customer preferences, shepherding, a wool market and so on - the rare breeds will be there ready and waiting to have their now appropriate characteristics available to breed into commercial stock. This might be better feet, a double coat (if wool prices were to go down even more and allowing the new crosses to survive better outdoors all year), a short tail ( less prone to flystrike), ease of lambing (the northern shorttails have a wider pelvis for their size than other breeds so tend to lamb more easily), good and quick mothering (where shepherding costs may become too high to be able to intervene at current rates), finer or coarser fleece (depending on the market - remember how the fashion for wood floors has shrunk the carpet market), there are all sorts of traits within the rarer breeds, which were developed in different times, which will be of benefit to future sheep breeds - remember the Suffolk which was developed from the Norfolk Horn.
Breeders of these traditional breeds need to be able to live too, by selling their stock.
However, the price for meat sheep is bound to be less than that for pedigrees of whatever breed, and the price for poorly animals will be less than for good strong healthy ones. Most breeders of the rare breeds are raising stock primarily to sell on as breeding stock, and selling the meat of those that don't make the grade is a secondary product.
The vast majority of those raising rare etc breeds are not doing it to have a couple of pet sheep (which are usually not bred from) but are serious breeders raising good quality stock for other breeding enterprises. So comparing the prices of pedigree sheep, of whatever breed, with prices of meat sheep, again of whatever breed, is not comparing like for like. Pouring scorn on one type of enterprise against another just because you are unfamiliar with it is non-productive - both types of sheep enterprise are equally valid, but different.