Because PS3 had comparable $50, $60 and $100 promotions and didn't see comparable extraordinary growth? We're looking for anomalous factors specific to the 360. Specific to June.
Disclaimer: I didn't check my math, so my points may be totally off. LOL
Didn't the PS3 see a 56% growth from May to June? Going from 177K in May to 276K in June. If you apply that towards the 360's 270K in May you get 421K for June. So you see an extra 86K and automatically think something nefarious is going on.
Did you know that for the last 7 months of 2010, the were only 2 months (Aug and Oct) that the 360 did less than 440K according to NPD. Last June 2010 doesn't represent a temporary monthly spike due the 360 S, it led to an almost total reshuffle of top sales leader in the US. And the 360 did this mostly without Kinect.
The jump in Xbox 360 sales jumped from May to June jumped 150% while the jump this year represented a 90% jump. The fact is that the Xbox 360 averaged 295K console sold over the first 5 months of 2010. Now, the 360 has averaged 383K console over the first 5 months of this year. In comparsion the the Wii went from averaging 406K over the first five months of 2010 to just 295K in 2011. While the PS3 went from averaging 257K per month over the first part of 2010 to 283K for 2011.
Average number of total consoles moved in the first 5 months of 2010: 958K per month
Average number of total consoles moved in the first 5 months of 2011: 961K per month
Seems to me based on the numbers, the 360 S with Kinect is cannabilizing a huge of amount of Wii sales with the PS3 also cannabilizing but by a much smaller amount.
The 360 has become the console market month to month sales leader in the US and its replicating similar numbers to what the Wii was doing last year. No one was suspicious of the Wii posting number we had never seen before on a month to month basis. Why should we now suspect NPD figures for the 360. The fact is the 360 S turned the Xbox into the monthly sales leader during 2010 and now it has Kinect for all of 2011.
Now Im not saying the MS isn't doing something to artifically inflate their NPD figures, but there is more than enough data available to explain 507K in June other than unethical manipulation by MS. 507K in june doesn't even represent the best month this year for the 360, that would be 535K in Feb. And if MS is doing something wrong it wouldn't be related to actions just for June but something ongoing over the last year.
You also have to take account that unlike the Wii, the Xbox S with Kinect is probably the most attactive product to its own current userbase probably ever. You get a new smaller and slicker form factor, better reliability and new functionality especially considering the original 360 wasn't the most attractive console, was still huge even by Xbox 1 standards and was the faultiest console ever produced.
Forgive my grammar.