You forgot the salaries of the network technicians you wouldn't have otherwise. You now have to manage attacks on your infrastructure yourself. You left out ban

You forgot the salaries of the network technicians you wouldn't have otherwise. You now have to manage attacks on your infrastructure yourself. You left out bandwidth costs as well. Your servers will need to be replaced entirely every 5 years, and partially as hardware fails. It sounds like you're at sufficient scale that it makes sense. For most people, it doesn't make sense.