What was it when MS tried to sell lower specced hardware for 499? then 399?
MS lowered their price just at the right moment, and they have a great relationship with a lot of publications, hell nobody even noticed that their review copies of Halo:MCC were broken!
Anyway, my guess is it's not that simple to lower the price, you must communicate with your channel partners, give them time to sell their existing stocks (PS4s are selling well, worldwide they sell more than the XB1)... and it's not as if there was any pressure for the price to be lowered until November this year.
Now, obviously they need to react, if you pick your bundle correctly the XB1 is sold for over 120$ less than the PS4 (330 with 2 oe 3 games - 50 in store gift card amounts to savings worth thinking about).
Add to this the release of a few games (Destiny and Diablo III) that gave some people the impression of parity...
People on a thight budget made their choice according to price, that's it, it makes sense, there is no fanboyism in seeing this (I prefer the PS4, but I am not about telling people what to do with their money)...
I don't think FH2 and the broken Halo:MCC did it, the XB1 has no game library advantage.