So this film wants us to believe...
That rich people would hunt their fellow man for amusement and hack sick old men to death in their dining room with machetes, simply because they could? I've met quite a few rich families, and maybe I'm being naive, but I'm pretty sure that there was more than the lack of a "Purge" keeping them from turning into serial killers.
No doubt such a scenario would draw out a couple of sickos who happen to be wealthy, but this movie sets it up to seem as if the waitresses and average joes of the world are still normal, while the well-off have collectively and suddenly developed a sadistic bloodlust.