Tipping a locksmith

I think the recipients of tipping are customarily limited to low paid employees who depend on that extra income to make a living wage (delivery guys, waiters, etc.). I’ve always had the impression that a locksmith business is basically a one-man man operation. Assuming that’s the case, the guy has quoted you a fee to do your project that includes coverage of his overhead, his own hourly rate, and a profit margin. I can’t imagine why tipping would be either expected or customary under those circumstances. Even if the guy who did your job is an employee of a larger firm, locksmithing being a highly skilled job, he is most likely being paid a quite substantial wage.