It is not, I already checked it with iPad4, unfortunately Rift optics will not work, you would need another optical system.
Yes, there is no way you can currently hit 400$ price point with two screens, and I think Oculus want to stick with the price very much. Also they would need to have two video inputs, or have a special board which will drive two screens as one digital input, but then it is additional latency source.
However, there are also these guys, which have similar design as a Rift, but use two screens and fresnel lenses, no info on target price btw:
http://www.roadtovr.com/2013/08/14/infiniteye-210-degree-hmd-prototype-contest-vote-7508