Costco is by and large its own supplier. Where there is the most shortages is in the b2b market (business to business). Consumer facing business are doing everything they can to hide shortages from you, and it takes a lot of extra leg work to keep end consumers from seeing the issues. Because you the consumer are being shielded from the reality you might see it in different ways. Things as subtle as going to a restaurant and the knives aren't the same for everyone at the table (because the restaurant bought the knives they could get their hands on).