I stumbled upon a great description of how you can go bankrupt in 45 minutes due to a manual deployment process. The most relevant part of it:
Any time your deployment process relies on humans reading and following instructions you are exposing yourself to risk. Humans make mistakes. The mistakes could be in the instructions, in the interpretation of the instructions, or in the execution of the instructions.
And no, it's not just application deployment. A similar disaster could happen in your network.