This is a usability benchmark of the homepage and category navigation of 100 top e-commerce sites. You’re currently navigating by page type (Top-Level Navigation). You can also navigate by case studies.
On this page there's 8 highlights (pro only) outlining what Costco are doing right and wrong. The screenshot was taken September 30, 2016 and depicts Costco's Top-Level Navigation and Intermediary Category Page.
In total, 6 of Costco's pages have been benchmarked across 79 usability guidelines from the Homepage & Category research study. See full Costco case study.