The 360 was already at $300 as well.
Can you point to anything in the data that suggests that the Kinect was more responsible than the 360 S for sales levels from Nov. 2010 onward, or that it had any measurable impact at all past the 2010 holidays?
24 million Kinects sold in just over 2 years, reports in 2011 stating 2/3 of console sales were the Kinect bundle, it was aimed at a different audience than the existing 13-30 year old male demographic and Microsoft shifted their content and marketing from "hardcore" to "casual".
You're the only person I can think of who doesn't agree that Kinect was a massive system seller and the primary driver of 360 sales from holiday 2010-2012.
The Kinect selling a lot of units doesn't prove that it shifted a lot of 360s by itself over a long period of time. I even argue that being bundled a lot during the Dec. 2010-Feb-2011 period doesn't prove it, either (also, that two-thirds claim was from Mike Pachter and was for Feb. 2011 only, not the whole of 2011; he also claimed half of 360 sales in Dec. 2010 were Kinect bundles). There just isn't any evidence in the overall sales data to suggest the Kinect brought in millions of additional customers that otherwise would have never bought a 360 (presumably mostly the "Blue Ocean"/casual/non-gamer types that supposedly were the sole reason the Wii succeeded), nor that it was the primary driver of 360 sales from Nov. 2010 onward. A lot of 360 sales in the first few months after Kinect's release being Kinect bundles could just as easily been regular gamers that hadn't yet bought a 360 and thought it was a good added value. After all, the Kinect by itself was $149, so the $299 4GB bundle is a damn good deal. It could very well have been a "Why not?" purchase, and a lot of people who were in the market for the 360 once the S was released could have spent their $299 on either a Kinect bundle or a 360 with a 250GB HDD.
Furthermore, to argue that Kinect was the primary driver of sales from the Nov. 2010-Dec. 2011 period, you'd have to argue that, unlike the PS3 Slim, the 360 S would have not been capable of keeping sales steady by itself past the first several months, and that without the Kinect the 360 very well could have been down considerably in 2011 instead of continuing to have strong sales.
The data we have clearly shows slimline models had a strong and immediate impact on sales for both the 360 and PS3. The data shows that Kinect improved the 360's YoY increases a bit in the 2010 holidays, but nothing suggesting continued boosts toward sales afterward, similar to major software releases, which similarly provide short-term boosts to sales.