In this context the actual answer is that a "consumable" item is one that is interchangeable with another, i.e. the marketplace generally sees HDD's as all being very much alike.
Hence why PC manufacturers like Apple may put Toshiba HDD's in their Mac Mini's for 3 months, then get a better price from WD for the same size drive, so then use those for 3 months, then get a better price from Seagate, and then use those for a few months.*
Price is king, as the product is seen as interchangeable with one another.
Much in the same way as raw materials like coffee, tea, sugar, coal, oil, natural gas are all seen as consumables to be traded on markets, to be eventually sold-on to processors who "add value" to the product, often by differentiating the raw material into a refined product — like HDD's are with high-priced Apple computers(!) or coal/oil/gas is when turned into electricity to be sold on for profit to end consumer.
(*although, we all know some models of drive can always have a run of failures, and thus the PC manufacturer may just buy another companies model instead, as, when, and if needed.)