None of those payloads can be had for a few thousand dollars.I used to know a guy (he died a couple of years ago) who was a retired testing engineer for a global manufacturing company. He had a home workshop that would be the envy of many small countries and thought that drones were the coolest things ever.
I'm sure that guy could, with a few thousand dollars worth of online purchases of computerized drones, have made weapons that could bring down Western society. Delivery some weaponized anthrax or radioactive material to the precisely right place at the precisely correct moment.
Was this assassination a drone strike?
I'm glad I'm old.
Tom
Going for a more dispersed target though I can see destroying the US with a price tag in the millions with no need to go into the WMD realm. Probably tens of millions if you are going to do it with prepositioned equipment so your people can get away before the strike. All targets are completely unguarded.