Certainly true that large volume retailers pay less than small dealers, but that's true in any industry.
When I bought my D50, I really wanted to buy from my local store but I bought from Beach Camera. I levelled with my local guy and asked if he could match the price or even come close to it, and he said "if I were to drop the price, which I would, I still couldn't come within $100 of the Beach price even if I discount it to my cost" Now before y'all get mad at me and tell me I'm an a*s for not supporting my local, I would have save that I'm a poor college student and couldn't make the $150 difference work, but rest assured that once I have a job I'll be purchasing from my local store
But anyway my point is that dealer markup is minimal at local/small dealers but that beach and B&H etc can sell for so little because they move a LOT more volume than those dealers and hence get commensurate discounts. All this means is that manufacturer markup is high on electronics, whereas retailer markup is high in other industries (see fashion).