I've seen reports of the new Pi ZERO being sold by authorised resellers for EURO 12+ plus shipping ...
But yes, volume purchases normally result in lower pricing, but notwithstanding the Pi ZERO using the "older" processor, I am not sure how far below the listed price the price can go. Are they getting the processor for free? The footprint of the PCB would itself cost about $2 at a dirt cheap PCB fabricator (OK given that would not be for volumes)!
I looked into ordering one it appears what a lot are doing is bundling it with cheap items. This allows them to sell the 5 dollar item for much greater profit. They include cheap accessories... and double the price if not more it seems.
So could be a bit till truly can get just the pi zero for 5 bucks. It's kinda scummy of so many to add accessories to get greater profit... but guess that is buisness.