Computer resellers, especially the smaller shops selling clones in the early days were also prime targets for marketing, who then repeated the message onto their customers.
I also add that people buy and upgrade their system more often when a new version of their OS comes out. It's the OS's and their accompanying software that sells the majority of computer systems out there and not so much the hardware determining the sale of the OS.
The result? Probably OSX would have the current windows and OSX's share, Linux would be with it's 2-3% and windows would be a distant history.
Also remember that OS X wasn't even around until 2001 and windows already had a dominance in the marketshare because of it supporting applications. The biggest reasons that people do not switch is because xyz OS does not run their apps. We have all seen those reasons "I'd switch but xyz isn't available on zyx OS" given too many times to count. Apple was still playing around in the System 1-9 era. When Windows 95 debuted it effectively took all of Apples OS advantages and matched them but still allowed people to use their old DOS based applications. There were also periods in Apple history where they did license out their OS's and allowed clones to be built. Those clones had hardware prices often equal or lower then their PC counterparts and those companies still failed to make any appreciable change in marketshare. Commodore and Atari both had far superior OS's as well back in those days and were one some of the cheapest hardware to be found. Even they still fell victim to the Windows movement because other then gaming they didn't have much at all in the way of productivity software. MS courted that market, gained acceptance by the corporate sector and started their road to dominance.