Where you say “to some extent negotiable” (paraphrased) could we regard it as the quantity unit corresponding to a price, and that a different and likely higher price might apply to orders of smaller quantities? In which case, knowing the tiers of quantity and their corresponding prices would enable us to find the best order pattern, trading off price, wastage or inventory holding cost, and lead time.

What you are describing is frequently referred to as 'price breaks'. Price breaks can indeed be seen as a more general flavor of MOQs. In practice, tthere are two flavors of price breaks: merchant and fiscal. See also https://docs.lokad.com/library/supplier-price-breaks/