[mdorazio]

They actually list their margins in their normal SEC filings. For merchandise it's usually around 11% on average. Obviously it will be higher or lower than that for specific products. Costco is able to have margins way lower than retail average (Target runs around 28% for comparison) by having much lower per-revenue dollar operating costs and by doing an absolutely stupid amount of revenue per location (a single location will average close to $200M in sales per year).

[Animats]

Costco has been annoying the drugstore industry by marking up the drug section at the same markup as the rest of the store. Markups at CVS, etc. are much higher. Costco has a smaller selection and only sells the big sizes, so it works out well for them.

[jmchuster]

14% markup on Kirkland Signature and 8-10% on everything else.