I think you're applying the wrong model here. War is a zero-sum game. This means that if the target is worth "X" to defend, it is also worth "X" to attack. So "X" just gets cancelled out, because it is the same on both sides of the equation. So the relevant variables here are the cost of attacking ordinance versus the intercepting ordinance, which will always be much higher. Therefore, Missile Defense can never sustainably work against a peer-opponent's saturation attacks, only against a much weaker opponent. If you can't destroy your enemy's ability to attack and saturate your defenses, you will inevitably lose.
Bringing this back to the Middle East, this is why "Israel," in its current form as a apartheid state, has no future. Eventually, it will need to accept a "One State Solution" model where Jews are a minority. It will accept it the easy way, or the hard way. Because for the entire Muslim world, from Morocco to Malaysia (the imminent demographic global majority) no other solution is ultimately acceptable to us. Temporary ceasefires and agreement's aside, this land is a strategic piece of real-estate that we will not accept in the hands of any other civilization, period. The math of the situation is this: "Israel" is surrounded by Muslim states that are currently weak, but this is a temporary state of affairs. Muslim nations will eventually get their act together (God willing), and at that point, nothing will save "Israel" and no one is going to come to its help.
p.s. Israel boasts of its "nuclear triad" as its ultimate protection, but it is too small a country to have any effective deterrence. I can literally see most of its nukes on Google Maps. And its diesel subs tied to a couple of ports aren't going to help it either. "Israel" is a hard fortified target for sure, but it is far from invincible against a competent foe.