They want a wage of $10.10 per hour? I bet a Costco employee starts around $10.20 per hour.
"Costco pays a starting wage of $11.50 an hour, gives most employees healthcare and other benefits, and has not switched to the model adopted by many big-box retailers of using temporary firms in warehouses to keep costs low."
A higher minimum wage costs Costco nothing and hurts their competitors.
I'm not saying they don't have good business reasons for this, they do, but it isn't all pure business upside for them.