Sacrifices include things whose loss is counted. The loss associated with circumcision make it appear to be a sacrifice, but it is a mark of a covenant, not a sacrifice. Then Zipporah took a sharp stone, and cut off the foreskin of her son, and cast it at his feet, and said, 'Surely a bloody husband art thou to me. . . The presence of blood in this ritual is very important. The blood caused by the operation is considered holy blood.
Blood is a symbol of life.
In circumcision, the blood symbolizes the beginning of a Jewish life. In Orthodox and Conservative Judaism, male converts who have already been circumcised are require to participate in a Bris where a drop of blood is pricked from their penis, symbolizing their acceptance of the covenant. In Judaism, blood is often seen as polluting. Blood is carefully removed from meat before eating and menstruating women refrain from sex for seven days. These two instances are examples of blood, representing life, being separated from instances of death, or the loss of a potential life.