There's many people who go out and get quick Christmas gifts. Would be silly to raise the price in my opinion.
You'll have parents set on buying the console only to see that it's $50 more in comparison to when they were doing their research on how much it costs.
It would be sillier than what MS did back in January in my opinion since January isn't a big month for console sales like December is.
But then it's the 20th, they don't want go to the mall again, and "it's only $50".
Maybe BF/early december buyers are price-sensitive, and late rushers are just plain desperate?