Because. Simply because they can. They have next to no competition.
Now, if they would only make a dual batttery charger for the LP-E6(N) batteries. I think they would find a larger market for them than they might initially think.
My apologies for the somewhat flippant wording of point 2 in my original message. If you ask an economist what the purpose of a business is (or consult a macro economics text that deals with the subject) the answer you will get is the one I gave. The purpose of a business in a free enterprise economy is to maximize the wealth of its owners. All decidions should be based on achieving that goal.
One of the things the business owner does in pursuit of that goal is to set prices using a demand curve (a plot of price versus the number of units that will be sold at that price) such that total revenue is maximized. I assume that a company with the resources and experience of Canon has a good idea of the shape of the demand curve for each of their products and sets prices accordingly.
You both are all wet! Canon sells a million Rebels. They sell a thousand 1Dx's. It is simply economies of scale. Plus the fact the gear is aimed at a professional photographer. In other words it is built to take day in and day out use.
Do I wish they were cheaper, of course but it is what it is. If you want cheap buy a Rebel and its accessories.
And remember there are really only two competitors in the professional camera market. Canon and Nikon. All the rest fall well short of the gear these two companies produce. Not in line-up nor in quality. And don't bother with the, "I just bought a multi-mega-dollar Sony (fill in the blank) camera and now I am a pro photographer." Not so.