You'd loose money. I've met many Costco employees. Most were either high-school students or older people without degrees who simply applied for the job or were referred then got through an interview. They care more about whether you'll work hard than anything else. Then they tend to stick around longer since they get paid and treated really well so long as they work hard. Lots of retail workers would like a job at Costco or a similar place but there's just few openings since people don't quit often.
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.
When you are willing to pay more, you can purchase higher quality; this is as true for labor as software or electronics.