Well, a quick look at Target's web site reveals a nifty Virgin Mobile model for 89.99. So, about 666?
But you are quite right. This story is alarmist nonsense. You only need two to trigger a bomb remotely, and a careful terrorist would buy them one at a time at different stores.
It would be interesting to know what use the buyer had in mind, however. I doubt it was reselling on Ebay. If it costs $90 at Target, I'd expect to pay $45 on Ebay.
Maybe he makes it up in volume?
Seriously, it sounds like a money-laundering scheme.
My first thought when reading this story was... who ordered that much stock of these phones? As you point out even at 100/each they would've had to have had hundreds of phones in their inventory... I wonder if they were all the same brand/style or whether he bought out ALL their inventory.
Seems to me like a LOT of phones to have in the stockroom, but then I'm not familiar with Target's ordering procedures/inventory management...