The aliens should consider changing the rule to anyone with a financial value that has a z-score of 2.33 on a bell curve relative to the rest of the world's population.
Given the aliens have a big appetite and understanding that this would eventually wipe out the human race, perhaps limit the numbers of humans that can be eaten to the birth rate of humans so that they create a sustainable supply of food.
Eat the rich!
That stew needs more carrots.