It shouldn't. Because it has. According to Microsoft, the expansion has "eclipsed first-day revenue for all previous downloadable content on Xbox LIVE". Which means more money was spent on it than any other piece of DLC in its first 24 hours on sale.
Kind of meaningless without sales figures or a previous record holder to back it up, but then at least other games now know who's top dog when it comes to DLC cash money intake.
Take that, horse armour!