I seriously doubt that any manufacturer, especially one with such a diversified product line, can say with certainty what one particular product costs them.
I'm not suggesting that they don't assign a cost to the product, I'm just suggesting that it is inevitable that the assigned cost has to factor in a number of assumptions that are not so easily segmented. Certainly, for their own internal accounting purposes, they would try to keep the camera division costs separate from the office machines division. And, I'm sure they try to segment the costs out as much as possible within a division – calculating real costs where possible and assigning shared costs as best they can.
But, costs don't fit neatly into clear assignments to individual products. Just use sensor research as an example. At some level, the research benefits every sensor they develop from the smallest point and shoot to the 1Dx. The cost of research unique to a particular sensor or format can be assigned, but the embedded costs of having a sensor development division must be allocated over the entire product line. Product development research must also be shared across products. The allocation will be done using hundreds of assumptions, many of which are made according to the overall goals and objectives of the company, not necessarily based on what percentage of the entire product line an individual product represents.
Ultimately, Canon is a single company and that means that various divisions must supplement one another depending on current market conditions, so that the entire product line survives over time. Just this spring, in their shareholder call, Canon stated that the office machines division was down and profits from the camera division were able to offset those losses.
This doesn't mean that Canon will or can lower prices. It doesn't mean that the $2,400 figure for the 5DIII is right or wrong or that they haven't assigned that number to the cost of the camera. It means that it's a little crazy to try to say "this camera costs this much to make" and even crazier to say "Canon is ripping me off because this camera should only cost this much."
In the end, the only relevant cost is the cost the consumer is willing to pay.