A 6990x2 is two SEPERATE video cards... it denotes someone using two 6990 video cards in Crossfire mode.  Just like a 6990x3 denotes someone using 3 6990 cards in Crossfire mode.

So @ $722 per card your total would in fact be $1444, not misleading in any way.  Keep in mind that the MH/s are averages based on user input, so YMMV.