No, 10.x.x are not service packs. The simple fact is that OS X has its own release/price structure. Trying to translate it into the way Microsoft does Windows releases is meaningless.
What the hell are you going on about?
10.6.0 = Windows 7 ( Windows 6.1)
10.5.0 = Windows Vista (Windows 6.0)
The .x on the end is the service pack itself, that is no different than Microsoft having 6.0.buildnumber instead of having 6.1.1
Good lord, stop spreading lies - its a pretty easy damn system; Apple has NEVER charged for service packs.
Apple's support policy maybe crap - but they've never charged for them in the literal manner in which the previous poster spoke of.