[lil miss molly]

I was looking for some insight on chocolate yorkies.I have been debating on getting one but they are so expensive.Why are they so much more then the standard color.Also are there any health concerns with this color mutation?I have asked the breeder questions but I am not sure if they are telling the truth or trying to sell me a dog.Also I have heard that the chocolate yorkies should reproduce if this is the case them the breeder should not even be doing this right or wrong?