We have a lot of customers who go to a hardware store or a box store to have a duplicate key made, and then they come to us to have it done right.
Remember that a locksmith is in the business of making keys. There are several differences when you purchase a key at a locksmith versus elsewhere. First, locksmith key machines are better. They are generally better quality and they are always kept calibrated. Most locksmiths calibrate their machines at least once a month if not more, to ensure that the copy that the machine makes is as close to the key given to them as possible.