Surface Pro 3 should be compared to rMBP 13
To be honest I don' understand why everyone is comparing the Surface Pro on price to the macbook air because of their physical similarities as ultraportables.
But as I see it there are more similarities that would actually affect cost between the Retina MacBook Pro 13 (late 2013) than with the MBA. The screen quality and processor to just name a few. The reason this comparison is especially valid is Apple switching the 13 inch model to the U series processors which should be more or less the same than what is inside the Surface Pro 3.
Lets compare the second tier rMBP and the third tier Surface Pro 3. In both cases you get a i5 dual core U processor, 8 GB of RAM, and 256 GB of storage. The price difference is 1500$ vs 1430$ in favor of the Surface with a type cover. The surface is much lighter, thinner, has both touch and pen input, and has 2 cameras. The rMBP has a slightly larger screen, better graphics, and PCIe Flash Storage. So the performance should be slightly better on the rMBP but it is more expensive and much less portable. This really puts the Surface Pro 3 at not a super high price point imo.
But mainly my point is that the cost of a high quality screen is not being emphasized enough and this comparison makes much more sense to me to bring more specs on par with each other.