“If they used an inert gas they wouldn’t expensive chemicals that are difficult to obtain.”
I disagree. Inert chemicals still means some sort of sealed chamber, with a window for witnesses to watch and medical gadgets to tell when they’ve croaked. This is still costly.
Just take one of the guards hand guns, take a bullet that would ordinarily be used for qualifying, take the condemned to the morgue and just do it. The ME can certify the death and we they are done. Costs are really minimized.