They pull people out of high schools, retail jobs, etc. They wont hire outright idiots but there's no IQ test or anything. Think about it another way: these people are going to Costco because they lack what's needed to get higher-paying jobs requiring degrees or trade schools.
Costco reps themselves already explained the extra pay was just incentive and that they believe in living wages. They also cancelled the ad bugdet specifically to give that money ("6% of revenue") to workers instead thinking good workers are better than advertising for customer retention. So, they consistently believe paying & motivating workers has highest benefits. They also pull from barely-educated sources who probably have above-average intelligence or character but still the common, low-rung pool of labor.
Costco reps themselves already explained the extra pay was just incentive and that they believe in living wages. They also cancelled the ad bugdet specifically to give that money ("6% of revenue") to workers instead thinking good workers are better than advertising for customer retention. So, they consistently believe paying & motivating workers has highest benefits. They also pull from barely-educated sources who probably have above-average intelligence or character but still the common, low-rung pool of labor.