Let's look what the REAL photographic differences between the RX1 and the NEXt best thing. The only mirrorless camera with similar sensor resolution is the NEX7. The only lens you can currently put on it that comes close in equivalency is the Zeiss 24mm f1.8.
BUT it is really not equivalent, is it? Afterall, DOF is noticeably shallower with the RX1 wide open. To have the same DOF on the NEX 7, the Zeiss 24mm would need an imaginary aperture of f1.4 (or the RX1 could be stopped down to F2.5 in reality). So we can say the RX1 is a full 2/3 stop faster in the lens. And since the front element of the RX1 is considerably larger we assume it should also have THEORETICALLY higher resolution. Whether it really does and whether it matters in practice is another matter.
Also, given the sensor size differences we can assume the RX1 will deliver ~ 1 stop better performance across the ISO range. This has been the historical pattern of FF vs. Sony 1.5 crop sensor cameras.
Finally, the RX1 has a base ISO of 50 vs. 100 on the NEX. Again another stop. (UPDATE: I have been informed ISO50 is an EXPANDED value so while it has its uses, lets call it a wash for now.)
Bottom line is an extra ~$800-1300 buys a smaller/lighter camera with almost 2 stops extra performance at its default levels. Now if you are the kind of photographer that finds that valuable and is not limited by the single focal length lens, the RX1 is not only a smart buy, its a steal.