We raise a lot of English orpingtons. Yes, we have had some that just pass away between 4 months and laying age. Most of the ones we lost were right as they were maturing and they were going to start laying. If they paid $600 for a pair, I'm going to guess they were a pretty rare variety. The problem with the rare varieties is there is no genetic diversity in the US for them and we have to be diligent to not inbreed too close. Yes, line breeding can be the strongest tool to have in a chicken breeders arsenal but you have to have a breeder that does it intelligently. If you breed brother to sister for too many generations, your asking for troubles, weak hearts, enlarged hearts, etc. Doing it one time can be ok, Then you breed chkldren back to parents, cock to pullets and hens to cockerels. Then neices and nephews back to the original birds. The problem we are running into is the importer starts, sells eggs of chicks from those birds. Their so expensive, the new buyer just gets 2 or 3 birds and can't cull birds like you would normally. They then hatch birds out of those siblings, the price goes down a little bit when they sell their chicks and it happens again and again.
