Not quite the scenario from my parent. They said "high cost weapons taking out air defenses". Whatever the US equivalent of an Iskander would be (I used a Tomahawk as an example), the S-400 (i.e. Patriot "equivalent") would be used to defend against it at first/in his scenario.
If you want to turn it around, sure. Let's see how you'd want to take out a Patriot: high cost weapons, like an Iskander might try it? Costs about as much as a Tomahawk? Would need multiple ones, because the Patriot would defend itself against even multiple ones? But the Patriots cost as much and you want multiple interceptors for each Iskander sent its way?
What if I could send, for less money/resources, a drone swarm that also takes out the Patriot or at least expends more money/resources in interceptors shot from it, than I had to spend on the drone swarm?
I totally agree, it's "just a race". If I build an offensive drone swarm for $x, which is less than your high cost interceptors, you better build an "anti drone whatever thingie" (which might be anti-drone drone swarms) that's even cheaper.
But, thanks, essentially you're agreeing with me: Don't use your high cost stuff to take out SAMs and then use cheap drones. Instead, use cheaper stuff to swarm it out of existence. Just gotta be faster at being cheaper. Doesn't matter if you're the attacker or defender.
Zerg vs. Protoss.