Inventory in a warehouse does not have the kind of cost you think it does. Most of the "cost" people talk about are hypothetical profits that a different product occupying that space might generate in the same time. The real costs are insurance and warehouse leases. Per unit, it's almost nothing.

A company like Apple could easily stockpile months worth of inventory and never even notice the real physical cost of storing it.

Opportunity costs, or any other "virtual" cost, are still meaningful figures.