If the wholesale price is down, and the retail price has yet to fall, someone in the middle must be making a profit. The article seems to imply that nobody is, but the margin must be going somewhere.
Example:
* I buy inventory for $5, sell it for $10.
* I buy more inventory, but it's gone up to $9. I'm selling for $13, but still have some $10 on hand.
* Wholesale plummets to $2.
Until I've sold my on-hand inventory, bought more at $2 and sold that, I'm not making any margin, regardless of how low wholesale drops.
I imagine the shelf-life for some stuff is short, but maybe longer for others.
Ie Tesco in Europe had record income for past year or two, as did most other mega chains. It a mystery why...