“The guns and ammo he used can be had for under $2,000 total.”
If you are a ‘smart’ shopper, perhaps for under $10,000...
He bought guns at gun shops in the area...top dollar...maybe $2,000 total if he got any kind of a deal. Ammo...approx $.75 to $1.00 a round, and it is reported he bought at least 6,000 rounds. His magazines, several hundred dollars...maybe $5 or $600 total. Add all this up, then start on the other stuff...the hidden stuff
Standard costume stuff ~ you can get it all, plus a gas mask, for under $100.