The intercept cost is now not only the cost of the interceptor, but also the cost of the flying hours of the launching platform, and the risk of losing the launching platform.
If you equip even some of your Shaheds with AA missiles (cheap manpads with autonomous IR target acquisition and guidance), like is already happening in Ukraine, the feasibility of APKWS becomes problematic. The technology is developing fast these days.
But ground-based platforms work just fine and cheap enough to scale up the deployment to cover the big area.
The big advantage of APKWS over interceptor drones is the rocket engine, they are much faster and can catch Shaheds within much bigger radius or within much smaller timeframe than interceptor drones.
Second, it is rather short range, and that range is helped significantly by the speed and altitude of the launching platform. Launching from the ground upwards would significantly reduce its range, which is anyway just a few km.
Due to the short range, you will need a densely distributed significant numbers of them, and still be in danger of saturation attack (the attacker can saturate one route, you have to be ready for all possible routes). Having a carrier platform allows the missiles to be quickly brought where they are needed, so overall you need much less of them (still too much, as having enough carriers in air imposes limits as well).
You can have longer-range ground missiles, but then the costs rise. Also, I am not sure how feasible/robust is to laser designate air targets from the ground. I suspect it does not work over longer distances, i.e. you need a more sophisticated and costly guidance system/sensor suite on the missile.
The beauty of an anti-drone drone is that you have a much more robust human-assisted guidance, for cheap (camera and communication link). With advances to AI, even that human and communication link are becoming obsolete...
With rocket propelled missile you have much faster closing speed, and quite limited energy budget - essentially you have to make a correct decision fast and precisely, otherwise the missile is wasted. With a drone, everything is slower and easier to correct.
On the other hand the latest development with drone interceptors is rocket booster to quickly bring in within Shahed. So I guess there would be a convergence between APKWS and interceptor drones.
