I'm sure Canon only tacks on their actual cost of adding IS, out of the kindness of their hearts.
I really wish Canon or Nikon would just cave in and offer in-body IS, then whoever wasn't first will soon follow, and everyone wins. There's really little reason not to offer it; if in-lens IS is as superior as they claim they should have no problem selling IS lenses to the more demanding crowd, and the hobbyists would get all their lenses stabilized.
ps: palmor, hasn't that thread been educational? We've learned not only that in-lens IS is clearly superior, but also that in-body IS makes your pictures noisier. Makes you wonder if the K-x would shoot clean ISO 25600 if that horrible, ineffective, noisy sensor stabilization crap was removed.