Would they like to? Probably. My 6+ was $850. Even after the cuts the carriers get, they still probably pocket more per 6+ than per iPad Mini.
Will they? I'm not convinced. I think they took this opportunity to push the Mini one notch down the spec curve, to make the higher-margin 9.7" model more attractive by comparison.
Why? There are people that buy both.
to small of a group of people to justify cost. If you own a iPhone 6 or 6 plus....i find the mini useless. Actually, for those who own a Plus....I think the Pro is where that crowd is.