Costco's average selling price is also quite high. Very few items sell for less than ~$10, and anything that would normally go for significantly less gets sold

Costco's average selling price is also quite high. Very few items sell for less than ~$10, and anything that would normally go for significantly less gets sold in Costco-sized bundles to keep the unit price up. One of their limiting factors for revenue per store is how quickly they can scan products at checkout. Higher ASP means more revenue for the same number of scans.