The answer is rather simple. What most people do not realize is that like Sony, Microsoft actually pushed the technical boundaries with the Xenon processor in the Xbox 360. The Xenon processor is actually a tri-core Quantum processor. Unfortunately, the engineering of the Xbox 360 was rushed, as many people have read, the RRoD wasn't the only problem to occur from the initial poor engineering on the console. There is, in fact, a much worse problem.
What scientists and Xbox Quality Control didn't know and are just beginning to understand is that in Quantum computing, odd numbers of things are dangerously unstable. What is happening is that in some circumstances the Xenon CPU of Xbox 360's implode into themselves, creating a micro-singularity that quickly destroys the console before running out of energy and disappearing leaving nothing but a tiny BB-like sphere.
Gamers have contact Microsoft about it, but you can understand trying to explain to support that your console just disappeared would be difficult. They're certainly going to question if it's their problem. However, with the increase in Xbox 360 console purchases this year, the problem has become considerably magnified.
In short. The reason you are seeing such huge sales of Xbox 360 consoles lately is because of the Quantum Singularity of Death (QSoD).
Unfortunately, Microsoft has no solution to this problem. Fixing it would requiring adding another core to the Xenon processor and subsequently replacing all consoles. However, since no customer had a console to turn into repair, Microsoft can't repair any of the broken consoles, and Microsoft support won't pre-emptively repair consoles. Customers can only wait until they break before Microsoft will repair them.
You can see the problem. The only solution for customers is purchase a new console when the QSoD happens.
Hope this explains it all.
