Hi,
in answer to your origional question on price. I have been looking at prices of different registered rare breeds recently and have found that a number of breed societies seem to use the avarage price from the previous years national breed society show and sale as a guide price.
Failing that contacting the breed society for an idea of price would give you a good starting point.
If any have gone through your local auction centre recently the centre may be prepared to give you an idea of price but they may require the lot number so you would need the sale brochure.
Personally I found that the price depended on supply and demand. If someone in the area has the breed that you want then the price is really what you can agree with the seller but to give you an idea, prices ranged from £100 to £200 a ewe depandant on breed, age, area, availability and pedigree if that helps.
Hope you find some