Lets suppose an agent sees a horse run who he likes. He calls the seller and says, how much. The seller will sometimes say, 300 grand and we will take care of you. Meaning they will pay you a commission. Sometimes you call up and say how much, and they will say 300 grand TO US! meaning put your commission on top of that or bill the other side.
Most guys who buy privately are pretty sharp. They have a pretty good idea of what a horse is worth.