That inc article is the only place I see those margin caps and it doesn't come sources. Other articles say that costco doesn't publish their margins. However,

That inc article is the only place I see those margin caps and it doesn't come sources. Other articles say that costco doesn't publish their margins. However, their financial statements do indicate an 11% average gross markup. But there are definitely plenty of products marked up more than 18% at Costco. Either that or they are paying way too much for some things.