>not one moving 200+ mph with an evasive trajectory
that is slow. Well under RPG speeds that current active defense systems (like Trophy) easily catch. And evasion on such a slow speed isn't a real evasion - at best 1m shift in 0.01 seconds - even cheap radar would easily track and would take it out with shotgun or machine gun.
> proper missile defense system or CIWS
that resolves, tracks and targets 30 cm diameter missile moving at transsonic speed at 2-4km. The point defense i'm talking about would need to resolve and target a 30 cm target at 10-20m distance (the tank or APC can take a drone warhead explosion at 5m distance) which is orders or magnitude cheaper/easier (you can even put a sub-$100 car radar or LIDAR onto a rotating plate similar like on Waymo car and whenever it picks something moving toward you at a distance less than 20m - just shoot in that general direction. Yes, infantry hates being around tanks with active defense in combat as shrapnel from the ADS hits the infantry, frequent story with USSR army back then in Afghanistan for example)
>Add a small rocket motor to the $20k drone for final approach and it’d probably top out at 400-500mph and it can use propellers to “jump around” randomly in its flight path so targeting it is nigh impossible.
Now you're trying to invent a jumping around RPG or Javelin missile. I agree that such development will happen too (though "jumping" at 200m/s is petty hard), yet it will not be able to always jump out of the shotgun grape shot cloud at that 10m distance. So, yes, there will be race between attack and defense, and my point is that single drone approach will be left behind pretty much from the start.
> cheap drone swarms is that their range is shit
50-80km communication and flying range is what we have already today. Communication - while staying cheap - can be extended further by retranslator drones (and for autonomous/AI drones the communication is much less of an issue - for example no need for high quality video, if at all), and electric drone-plane (not quad) can do up to 200km even today.
>I think saturation attacks are only going to be useful against static targets
I see quite opposite. Modern air-defense shoots down all single targets with high probability (except for stealth, which like $4M for one Storm Shadow stealth cruise missile). On the other hand - Pantsir-S1 can target simultaneously only 4 targets. A battery of S-300/400 can shoot only 12 missiles before reloading. Trophy and the likes easily shoots down one incoming targets and takes half-a-second or similar to get ready for the next target. And improving the simultaneous capabilities is costly. Where is saturation (horizontal scaling :) is an easy and cheap way to overwhelm/defeat such systems.