Two more sobering axes to introduce: cost and manufacturing capability.
Numbers are hard to find for obvious security reasons, but using the numbers most optimistic to the defender[0] suggests an adversary using a Fatah type hypersonic is spending 1/3rd the cost of an Arrow interceptor, and is launching missiles that are produced at a much faster rate. Interception is deeply asymmetric in favor of the attacker.
[0] https://www.jpost.com/israel-news/defense-news/article-82314...
The best missile defense is offsense: degrading the launchers, stockpiles and defense industrial base, with cheap stand-in munitions after SEAD, leveraging air and intelligence superiority. Expensive interceptors are only a stop-gap that buys you time for the offensive degradation. Expensive stand-off munitions, likewise, are a short-term stopgap until SEAD is complete.
Currently, we're using $1M interceptors to take out $30K drones. This asymmetry is here to stay.
The end game probably involves < $1000 autonomous drones that target IR or RF and drop something like hand grenades. On the defense side, there would similarly-priced interceptors with bolas, backed up with sharp-shooters for important targets.
At that point, it turns into a logistics problem that's much easier for the attacker than the defender. Iran's already demonstrated that one successful drone can do $100B-1T in damages, so a hit rate of 0.1% means a 1:100K cost:damage ratio.
That's a false comparison. You want to compare between the actual options you have, which are either (a) firing an interceptor (or several); or (b) repairing the damage caused by a non-intercepted missile.
There are too many potential attackers though, and not everyone is sane. So you don't really get a choice about it. The cost of the interceptors needs to be considered in relation to the cost of what it protects. If the interceptor means an attacker doesn't kill my kids then it was worth the cost. If the interceptor keeps a multi-million dollar building around then interceptor at a million dollars is still cheap, even if the missile it takes out was only $100.
Yes you should use diplomacy to ensure war doesn't happen in the first place. However if it does: they will send cheap drones and missiles at you in large quantifies.
Ah yes, but then you also have to add GDP + targetting/defense radii.
Great Britian alone has 10x the GDP of Iran. So an interceptor costing 10:1 is (at first approx) breakeven just for GB, who would have to intercept much less than the total manufacturing capability of Iran anyway.
Then you have every rich nation surrounding Iran as well. Let alone the USA who cannot be reached but throws their weight behind interceptions.
And finally "total manufacturing capability" is set to decline in any prolonged engagement with an Iran-like nation, but GB, western EU, USA, et al, are likely to only increase production if an engagement played out.
The math looks catastrophic on paper at 10:1, but I sincerely doubt that's the right analysis. An interceptor is worth what you're protecting, not what the attacking asset costs, so long as you can keep producing them.
Sobering how asymmetric Iran’s attacks on Israel are after Israel attacked Iran.
Calling a Fattah hypersonic is a misleading claim. It is simply a ballistic missile that reaches hypersonic speeds, which is different from a true hypersonic weapon in its flight path and ability to maneuver. This distinction is important because it makes it significantly easier to shoot down than something like a hypersonic glide vehicle or hypersonic cruise missile.
But I agree with your point that it does remain difficult to intercept and poses the shot-exchange problem.