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)!