Actually the xbox controller cost in the bundle must be really minimal. Build cost is probably 15USD or lower. And I doubt Microsoft is charging a premium at this point. Its in their interest to have
a really good relation with Oculus. So if they peddle away a few million extra controllers at cost cant be a big deal for them.
The integrated headphones and mic is a great addon. To have devs work towards one positonal audio target for the majority of the users will just benefit the whole ecosystem. Oculus throws millions of
dollars at VR audio research atm, so count on it beeing really good and up to par.
And for the people who still want to use their special audio equipement, you still can, as the headphones are detachable. Vive will ofcourse use a similar integrated way of doing their audio.