Were OS upgrades ever a significant profit center for Microsoft? Prior to the free Windows 10 upgrade, most users I know of would only get on a new version of Windows when it came with a new computer.
I never said they were-- those are new licenses, and accounted for by Microsoft as OEM sales.
I'm asking about Windows upgrade SKUs-- the kind that you'd buy in a box someplace like Best Buy or Circuit City or Office Max back in the day, completely separate from a computer. Were those ever a meaningful fraction of sales? Or, phrased differently, is Microsoft actually leaving any money on the table by making Windows 10 upgrades (both the Windows 7/8 to 10 and 10 feature releases) free for consumers rather than paid?