Yeah it's all bullcr*p, Microsoft told Gamespot it's not true.
It would be so lame if this was true, think about it, 25 Million each for a timed exclusive?
By the way, the word exclusive is over used the last couple of months/years, I remember in the store today.
Got the Bioshock case in my hand with "Only On Xbox360 And P.c!" on it, and we all know it's ported to the Playstation 3 now, so that line is irrelevant.