Depends on the breeder. Some people are just nuts. I had a friend telling me she wanted to rehome one of her girls. She ended up telling me she wanted to sell her for $2K because she was trained as a therapy dog. Well, shucks, don't tell folks you are rehoming a dog when you are trying to sell a full trained dog that has a "job".
To me, maybe there is a small fee to help the breeder recoup a little of the expense of raising the dog. Definitely the expense of fixing the dog. I had a breeder sell a dog to a friend for the exact price it cost to neuter him.
Anything more is just greedy to me.