I think this equation actually makes sense when only the same people/minds are changing the factors. If the same team is given the task of improving a product,

I think this equation actually makes sense when only the same people/minds are changing the factors. If the same team is given the task of improving a product, chances are they will be close minded and only able to tweak say security at the expense of the other two. To break this equation, you need a new paradigm, which often comes from outsiders adding their perspective. And open source is a great way to do this.