It isn't - deprecation of held goods is always a risk and if you're working on consignment then that comes with weird financial liabilities. If there's a flood and you lose your inventory it sucks - if there's a flood and you lose an inventory of consigned values then suddenly you're potentially exposed to paying market value for a number of items in addition to all the site damage you'll need to address. Capacity is one aspect of the costs of holding inventory - but breakage is the much more expensive consideration and consignment just makes it even more expensive.