Is the retina worth the price differential? I'm thinking so (still on the fence, waiting for ML release), but that doesn't make the rMBP actually cheaper, just means it has a better value proposition (which ends up being subjective anyway).
If we assume that one renews his macbook every three years (AC warranty limits), then I agree that retina novelty is worth the price differential. The dilema is whether the shortcoming ML release would fix all retina critical issues. If the time forecast to expect ML to fix all issues is higher than let's say 3 months, then I think it is not worth...
My 2cents.