You could get two sparrows for one penny. However, if you spent two cents you could get a bargain - four sparrows and an extra sparrow thrown in. That's how little value sparrows had. Jesus uses this simply illustration from every day life to make a profound point about God. He's saying that even this little, forgotten sparrow that's thrown into the deal is precious to God.
Many people today feel or are made to feel that they are as worthless as that little sparrow.
Perhaps most of us have felt like that at some time. We all need to be reminded that we do matter. We are not faceless, nameless beings in a vast universe. Jesus, our greatest authority on God, tells us that God knows and cares for us as individuals. Every person is of infinite value and worth to God.