Are you serious? If you did any research on your own you would know the differences. You would know that the QX series has been out for ages. Are you one of those people that think just because something's more expensive means it's better? The current QX's have had almost the same price for the past year or so, and they were top of the line until i7 came out. If you even read ONE REVIEW you would know the differences.
It's still expensive because people will still buy them if they don't do their research, because "oh my, it's the most expensive it must be the BEST!!!11!!111!one!1"
Bottom line: i7 is the latest and greatest. Even the budget 920 kills the old QX series for 300 bucks. Which is why we keep saying stuff about PRICE.