Delivering explosive payloads is a solved problem. Detecting humans is a solved problem. The hard part is reliably distinguishing enemy solders from friendly soldiers or civilians.
I don't have real numbers for anything, but I tend to do analysis like the above quite often when evaluating business models. It's usually within a factor of 2x to 10x of being correct, so please don't take it as anything more than that:
A typical round weighs around 40 kilos or 100lbs. For reference, from a quick web search, as commodities:
- 100lbs of TNT would be around $500
- 100lbs of stainless steel is around $250
I'm not sure what materials go in (I'd assume better explosives and worse steel), but I think $250-$500 is a good estimate for price of raw commodities (not including anything beyond that).
I would at least double that for having those shaped into an artillery shell, and add the cost of non-commodities (like a detonator), and you're easily at $1000. I would at least double that for the raw cost of distribution, sales, shipping, and logistics, and other overhead. We're probably at $2000.
At that point, toss in 30% profit margin for everyone along the way (30% to manufacturer, 30% to distributor, etc.). You're probably now around $3500.
I think that's a bare minimum baseline for what it would take to get a very, very dumb shell. This goes up if you want:
- Anything at all fancy or high-tech
- War profits
- NREs covered (building a factory, which might be idle 95% of the time and spin up for wartime)
It's possible to know where the humans are but be unable to destroy them with commonly available artillery payloads due to them being well dug in with overhead protection.
Drones are a solution to the targeting problem: the operator watches through a live video link, identifies the target, then deploys weapons. (Drops grenade/launches Hellfire/navigates into the enemy)
This is why, despite being technically feasible, we haven't seen drone swarms yet. You can easily build 1000 drones, but you can't have 1000 channels of live video over radio back to 1000 drone operators.
Delivering explosive payloads is a solved problem. Detecting humans is a solved problem. The hard part is reliably distinguishing enemy solders from friendly soldiers or civilians.