IIRC, Gyrojet testing was centered around intermediate cartridges for Assault Rifles, not larger things.
I suppose what's in my head would probably be more like 100$ than 20$, since it'd be functionally a homing micro-missile, designed to home on either a lased target or a drone's transmission. Like I said, not sure if it's actually feasible or not.
If it is feasible, it'd still be cheaper than the drones themselves are.
You're not getting a homing anything in 100$ range.
Something like that already exists, except in 40mm GL compatible variant.
Laser guided, compact, still nowhere near the range you need to use against the peskier drones, both for guidance and the munition itself.
It has an effective range of 400m, and needs the operator to lase the target by hand, which may be an issue with a moving drone 5km away, so probably need a beefier launcher that can have a computer do that too.
And the missile needs a seeker to see the dot from 5-10 km.
Back in 2012 two American defense firms (Nammo Talley and Raytheon) cooperated to develop a laser-guided 40mm grenade Three years later they got the concept working in the form of the Pike 40mm laser-guided grenade The original unguided 40mm grenade wa
strategypage.com
The Pike manufacturer (Raytheon) has not made public the cost of each round but given the cost of other small laser-guided missiles (like the 70mm APKWS) each Pike probably costs at least $3,000 and probably two or three times that. It could be useful for special operations troops but for most infantry, there are plenty of other guided munitions available, many of them cheaper and more destructive than Pike.
For anti drone use, you need to essentially upscale the system to MANPADS size again.
And here you go, modern, laser guided MANPADS exists.
It has just about the right stats for fighting medium drones, with ~7km ceiling and range.
It's used in Ukraine and reported to be very good at that.
The only extra thing that could be done here is to switch out the engine a bit for longer range and lower speeds, but then again, the engine itself is not the deciding factor behind the price of such weapons. It's the guidance kit.
The price of older MANPADS is in mid 5 figures, this is probably similar.
This puts it in high 5 figures per missile. Even if you cut the cost to low 5 figures with various unnecessary performance spec cuts, getting it down to subsonic targets only, that's still a very expensive weapon.