The client division, which markets Windows, generated operating profits last quarter of $2.48bn (£1.57bn) on revenues of $2.89bn, implying margins of 85 per cent. I suspect this varies heavily depending upon what part of the production cycle the current versions of Windows are in. Punching out copies of Windows isn't nearly as expensive as developing it.
But don't the cost for operating this division include that of devoloping the next versions of Windows?