I'm not too impressed with the examples given for surface Pro sales. Delta is an all Microsoft shop, that's well known. And the reason given for their moving to Surface Pro was that they didn't need to do much.
But, I have a friend who is an executive in IBM's enterprise software sales division. Recently, they gave him a tablet. Which one? Surface Pro? No, it was an iPad air.
As far as I can tell, enterprise wins for Surface anything, has been dismal. Consumer uptake if anything, has been worse.
In talking about selling a $500 tablet for $199, one has to remember that that's well below their cost. And out of that $199, Best buy needs to take its own profit. So Microsoft likely sold them to Best Buy for around $150, no more. That's a bloodbath! Even $350 is not more than break even, if that, when sold direct by Microsoft. But if sold by a retailer, Microsoft is again losing a lot of cash per sale.
Surface Pro tablets, as we know cost much more.
Unless Microsoft gives sell through numbers, we should assume that sales are another disaster.