> propulsion, warheads, arming and safety, QA, traceability, climate and shelf life stability.
You're entirely missing the point.
These do not need to be reliable for the scenario I hinted at. They also do not need to be armed.
They need to be large enough that if one of them is a higher quality rocket (not part of the $10k) that contains actual explosives, you have serious destruction on your hand. Maybe something that looks large enough for that will drive the cost up and we're talking $20k or even $100k instead of $10k.
The precise cost is largely irrelevant, as long as the total cost is a tiny fraction of the cost of a missile interception.
The point is you'd be multiplying the cost assymmetry by forcing a massively outsized response. Because if you don't try to intercept them, every future barrage will include a real rocket. If you do try to intercept them all, you'll be burning through massively expensive interceptors to take out a bunch of cheap toys.
If I was ever considering an insurgency, or a war, I'd be stocking up on vast quantities of toys, with the intent of making every radar constantly lit up by a number of possible threats.