let me parse this out a bit. first of all, sure, of course they aren't the high-end $2600 laptops. In that argument, most of the imac apple sells probably aren't 27", most of the laptops apple sells probably aren't 15", why draw the line here? Matter of fact-ly, they keep doing it because it's 1. easy 2. higher profit margin, 3. satisfy a given class of customers who will look elsewhere.
This rolls up to my next argument, I honestly have no idea where you guys are getting the idea that apple needs to re-invent the wheel to fit the 850M. I don't know about socket differences, but I know they are using the same manufacturing process which means the die didn't shrink and the size of the chip is most likely exactly the same. change in the pin layout is literally a change in the adapter which probably takes trivial work. Comparatively, it makes no sense for Apple to leave ONE BIG PART of a laptop empty, including the second fan assembly, just to satisfy their hatred for DGPU. money is money and if money can be made, it'd be dumb if apple won't do it. if DGPU is going away, it'll most likely come with an ENTIRE new re-design of the laptop, one that will actually take advantage of the almost halving of the thermal output.
Saying you can spend $400 more for a mac pro completely misses the point of a laptop. you can also spend the same now and get a much more powerful imac.
and no this is not the first time the 15" doesn't have a dgpu. this has happened before in the classic macbook pro.