The employer is paying you for the product, not the effort. I see no moral quandary here, nor any compulsion to notify the employer. They're getting what they want, that should be the end of it.
EDIT: And I would add, for anyone that has automated their job in this way...what you should really be doing is scaling it up, and finding other companies who are probably paying employees to do the same thing. Then start your own company that does whatever this task is as a service.
EDIT: And I would add, for anyone that has automated their job in this way...what you should really be doing is scaling it up, and finding other companies who are probably paying employees to do the same thing. Then start your own company that does whatever this task is as a service.