They could probably sell a plastic bluetooth, non-backlit keyboard that just snaps on by the magnets and fits the size of the screen, but has no communication through the ports for $29, then also sell the Type Cover for people who are willing to pay more for a nicer keyboard.The difference is, IMO, that the iPad is generally used without a keyboard. The overall number of keyboards sold is tiny compared to the overall number of iPads. The vast majority of people who buy an iPad will never want a keyboard for it.
The Surface, however, is a different story when it is running full Windows with a legacy desktop. People expect to be able to use that desktop, and the reality is that the experience is much better with a keyboard and mouse. Heck, there are even programs out there that you can't interact with without a mouse.
I think that Microsoft is doing the right thing by not including it, but I also think they are shooting themselves in the foot by pretty much only advertising these devices with the keyboard, and pricing that keyboard at a very high level.
Otherwise, maybe third parties will start selling alternative keyboards that fit the Surface for lower prices.