You are not completely correct - if you look at
www.linuxprinting.org you will notice that most Cheap&nasty Winprinters are supported as well.
Linux also has the advantage of not needing to hunt for the driver disk when you change to a new printer as most drivers are installed with the operating system - my father recently bought a cheap shop-clearance Canon BJC2000 printer (without drivers or manual) which I tested for him. On my Mandrake system I just used the CUPS WWW admin tool to add the printer and test it, to get it working on his Windows machine I had to download 3mb of driver from canon's website.