I too have the same Q on the pricing here. Not following why the the X-11 would be less than 21 or 12 unless it had something todo with recent groupon ?
Also wondering if XV-21 comes with both brushes as per usual package or only comes with the non Pet brush as pictured?
"Neato Robotics currently has four models on the market: the original XV-11 (green), the European and Malaysian XV-15 (blue), the XV-12 (white) and the XV-21 (purple). Despite the different model names and colors, all three 1x (11, 12, and 15) robots are identical, except that the plug at the end of the power cord varies depending on the locale.
In March of 2012, Neato Robotics announced its Neato XV-21, a refinement of the earlier models, which is white but has a purple laser head and dust bin cover. This model is designed for pet owners or people with allergies, and features a combination bristle brush/silicone flap beater in a swirl formation and a new pleated filter which is claimed to remove up to 3 times as much dirt as the original filter before clogging. However, none of the Neato vacuum filters are HEPA, including filters for the XV-21 model (as of June 2012). Owners of previous models can upgrade to the new beater and filter hardware for a cost of around US$60, and are also recommended to have the most recent system firmware."