Sale barns around here will not pull a single out of a lot just because someone only wants one or a certain one.  Not for a penny a pound, not for a nickle a pound, not even for a quarter a pound.  Sale barn owner would look at you and chuckle thinking you obviously were $hitting him. 

Once they hit the sale barn, there is no private treaty.  All animals will go throught the sale ring.  It is a matter of trust and maintaining a reputation.  You start doing sales on the side and suddenly nobody comes to the auction.