I did some searching, letter bombs were using 50g of RDX [1] and were able to kill a person so driving (and exploding) a drone with 171g of RDX into someone is more than enough.
If you take its 18km of reach (while I doubt the controls are able to go that far although with a 4g sim card this could be doable) you get a poor mans cruising "missile" for $1k. And there is nothing preventing (except the price) launching few of them.
I think that those drones are posing a real threat even more as probably the drug cartels have the money to realize it, if they can afford to build parallel cellular network [2], they surely can also perform this.
Their use case probably is not killing an average Joe but rather assassinations on high profile targets that are heavily guarded. And quite frankly I am really interested how bodyguards can tackle this as drone can literally fall from the sky, without any electricity being used so jamming (or frying electronics if feasible) wont work here. I think this is going to become a real nightmare in the future.
[1] 4g of RDX: https://www.youtube.com/watch?v=c6Qj1qSZDKg or 100g of "something" https://www.youtube.com/watch?v=X_664jlLwqI
[2] https://www.reuters.com/article/us-mexico-telecoms-cartels-s...