This table here shows how price cut and new devices release affected the sales and Gap of HD consoles. I didn't take the release date of 360 Slim and Kinect and Move into account since the 360 Slim was still selling at $300, no price cut there.
|The Event||Event Date||360 Total||PS3 Totals||Gap at Time|
|Before PS3 release||November 2006||5.16 Millions
|Before 1st PS3 price cut||November 2007||12.74 Millions||5.68 Millions||7.06 Millions|
After PS3 price cut and
before $200 360Xbox
|September 2008||20.00 Millions||14.32 Millions||5.68 Millions|
After $200 360 release
and before PS3 Slim
|End of August 2009||31 Millions||23.07 Millions||7.93 Millions|
After PS3 360 Slim, Move
and Kinect till today
|16th April 2011||53.11 Millions||49.51 Millions||3.6 Millions|
It should be interested to see what will happen after a new price cut from those consoles.
Edit:(corrected PS3 sales in last lines thanks Zgamer)