Okay, I know it is pointless, because even if everybody said that they don't know anyone who did this you would still believe the other way, because you just like it, but I will try to bring up one arguement that just proofes you wrong.
So let's say a significant number of sales are redundant. Let's say 20%, because it is easy to calculate with. That would be 20million unique Xbox360-users. The Xbox360 is still a software-selling-machine. Imagine the "real" attach ratio. The ratio right now is 8.1! So with a smaller userbase but the same amount of software sold, the attach ratio would increase even higher. That would be close to 10.0. So every Xbox360 users would have bought 10 games, which is definately not the case. There you can see, there can't be a significant number of redundant Xbox360 sales.
Same for Xbox Live. There are more than 14 million UNIQUE Users on live (probably 15 million after Xmas when the kids have the console under the Xmas-tree and actually start using it.). That would be like 5 million Xbox360s without Xbox Live. 75% of the consoles would be on Xbox Live. That is just not the case.
There you go, the number of people owning multiple Xbox360s is not that big, probably as big as the multiple PS3 users (One for gaming, one for BluRay).
Imagine not having GamePass on your console...












