Windows Enterprise is a superset of consumer Windows, so, given the existence of the former, the marginal development cost of consumer Windows is limited to the

Windows Enterprise is a superset of consumer Windows, so, given the existence of the former, the marginal development cost of consumer Windows is limited to the comparatively modest set of Windows features that few enterprise users care about — many of which are directly attributable to gaming, which, like Office, is another solid Microsoft revenue stream — plus any additional costs associated with producing and distributing multiple editions of Windows with different feature subsets. Moreover, I believe Microsoft no longer charges for consumer Windows upgrades because they save more money by supporting fewer distinct versions of Windows (with security patches and compatibility with other Microsoft products sold to consumers like Office and games) than they previously made on consumer version upgrades. Finally, the overwhelming majority of consumer Windows license sales are to OEMs bundling Windows with new PCs, and these licenses offload the burden of frontline technical support on the PC vendor. Taking all these things into account, it would actually surprise me to learn that Microsoft loses money on consumer Windows. As for "serious DRM", are you certain this would actually increase Windows sales enough to offset lost revenue (Office, Game Pass, search advertising, etc.) from consumers who would otherwise be running pirated Windows? So what to make of the 99¢ codec charge? My guess is lawyers: one could make a reasonable argument that there is no material difference between bundling HEVC with Windows and making it available as a free download for all Windows users.