Counter drones like anti-missile missiles need to be bigger than one would think and require much more energy, because they need to be much faster and more maneuverable than the drones they are hitting. That means bigger motors, higher discharge batteries, and a stronger airframe.
I'm fairly certain they would be more expensive than the attackers drones, and you would need around two orders of magnitude more of them than the attacker.
Smaller batteries since they don't need to travel far.
Nets or or even nothing instead of explosives, they need to stop drones not people.
The above two mean a lighter air frame.
The above 3 all mean more speed with the same motors (probably good) or less capable motors (seems like a bad plan).
Communications only need to be short range. Autonomy is plausible (but requires solving friendly fire).