I don't believe that there really is such a big demand, more like a limited supply. Therefore the dealer's allocation. But, they also get a limited allocation of Echos, Matrix, and Camry models too!
When I was shopping last October every single dealer I walked into had or could IMMEDIATELY deliver any color Priius I wanted! No list, no wait! Half of them mentioned that they have a $3-4K surcharge. When I mentioned that dealer X only wants $1000 over MSRP, they always said, OH, we can do better than that!
Just like what happened when the Pontiac Fiero, Mazda Miata, and Mini Cooper were introduced, it's all dealer hype!
Just offer them the price you are willing to pay. If you can have cash, a cashier's check or your own financing pre-arranged, then you have an even better chance of closing the deal quickly. Especially if you wave the paper in the sales person's face!