Costco employees are unionized. They are also insanely fast and very good. You cannot hire someone with those skills off the street, and the Costco wage scale

Costco employees are unionized. They are also insanely fast and very good. You cannot hire someone with those skills off the street, and the Costco wage scale reflects that -- a 5th year employee can easily earn double what an entry level worker makes. That wage scale is carefully negotiated between the union and the company to divide the value created by lower labor turnover and increased specialization/experience. The cost of the union is relatively low compared to the value created by having well-trained workers. It is likely that equally skilled workers could attain the same (or better) pay working for an equally enlightened corporation, but that would be a rather unstable setup.