The Ending Of The First Purge Explained

The most clever aspect of The First Purge is how the poor are coerced into sticking around and participating in the experiment, being offered $5,000 to stay on Staten Island with bonuses on top for additional participation — i.e., more cash for more kills. 

The fact that people put their lives and morals on the line for money has plenty of parallels to our real world, where the poor have historically been exploited financially. People are lured into disadvantageous schemes by the promise of short-term gains, entering into manipulative deals that aren't long-term beneficial. 

One government-sponsored example was the highly-unethical Tuskegee syphilis study, in which the federal government coerced people into signing up for medical experiments against their best interests. Enticed by the promise of free medical care, participants were kept sick for decades for the purposes of a scientific experiment. These sorts of deals are vicious trade-offs, entered into by people with no money and no options — and it's a phenomenon The First Purge represents beautifully.

The "cash for kills" concept is best embodied by the high-on-life crackhead Skeletor, who begins the movie as a terrifying agent of chaos before turning, by the movie's climax, into a militia-destroying avenging angel. There's a delicious bit of irony coloring the bad guys' demise during Skeletor's last stand in the housing projects, considering he wouldn't have been in a position to do away with the government's goons if he hadn't first been coerced by the government to kill.