Making assumptions about the nature of a thing without knowing the nature of it. We can't know how 'complicated' the answer is, so we can't know it's 'impossibly complicated'. It seems likely to be either the Intel deal being more than is 'recommended', or who is making the MB increasing the price vs 8750h MB, or a combination of those.
You are getting the only answers that can be provided. There really isn't any more that anyone can provide as it seems you won't be satisfied with any response.
Supply. Demand. Companies will charge what they believe the market will pay. Premium components fetch premium prices.
Sometimes the answer is "that is just the way it is".
Good luck finding your answer.