You have some weird way of thinking that offense/defense is like this fixed cost thing. It's a lottery ticket, and your costs estimate tries to quantify that.

The thing is when AI goes to hack 'all the things' it only needs to pick the weakest link in the stack and your house of cards falls down. The other flaw in your plan is that people make mistakes, a lot of them, all time, constantly, and saying I spend $x on security won't save you. AI already hacked Hugging Face with brand new zero days like it was nothing.

The real bad actors - malicious AI will find the one flaw, on that one server, in the corner you never thought about and turn your network inside out with it faster than it takes you to have the standup meeting about the weird anomaly detected while you all were at lunch.