BB guns can cost anywhere from $12 cheap single shot pistols to $300 electric automatics. If you just wanted to pick up a BB gun from a sporting goods store, it is about $30.
The cost of steel or copper BB is determined by how many you purchase. .175 BBs start around $2:50 for a few hundred and $5:00 for a large pack. Air soft BBs also vary in price depending on size and...