I don't believe that manufacturing cost have a direct correlation with retail prices.
Manufacturing costs (or rather, "cost of sales") establish a floor below which is "unprofitability."
I have manufacturing costs to produce the wall portraits and other products I sell. My large sizes do cost me more to produce than my smaller portraits. The difference in my prices between them are not in direct proportion to the difference in my cost to produce them, but the difference in my cost to produce them does establish the floor for each.
Canon will always try and get as much for a new model as the market will tolerate, and I'm certain that they would water down a product to encourage you spend the extra money to buy a 1-series.
That makes less sense than you think it does.
I think it starts with a misconception that if a rancher sells both horses and dogs, he cripples his horses to produce his dogs.
I sell both large and small wall portraits. Because I understand the artistic relationship between head size and format size, my small wall portrait is not simply my large wall portrait with less enlargement, and it's certainly not a large portrait with part of the print lopped off (it's not a "crippled" large portrait). I actually frame and pose differently when I know the end product is to be small. I do not do a full-length portrait in 16x20; my full-length portraits are done in a minimum of 24x36. By the same token, I don't enlarge a headshot to 30x40--my headshots will not be larger than 16x20.
I also have what are for me is an "economy" package designed specifically for a particular market that values my particular technique of art but can't easily afford it. I cater to them because they love exactly what I most love to do. They gush over it, they appreciate it highly, and they make me feel good. I don't take a high-end package and "cripple" it to make the economy package. My economy package is designed from ground up to give them the most "bang for the buck" and is, in fact, a wholly different kind of package.
For instance, because the economy package is photographic paper, it will be matted and glazed in the frame rather than merely framed as my higher-end canvas package will be. The economy package actually costs me more in labor than the higher-end package (which costs so substantially more in materials that it significantly overcomes the lower labor cost).
Canon Inc (that is, Canon Japan) has said that the 5D was created specifically for a particular market: Japanese "enthusiasts" who were still wedded to film (read: Elan users). The 5D is not a "crippled" 1-series, nor is it a "watered down" 1-Series. It's designed with the features that provide the best bang for the buck for that particular market--to get an Elan user to switch to digital.