the industry has predicted the demise of apple since 1979, and pretty much every year since then, with the exception of 1984. the single factor that has kept them afloat is their product. the motorola-based processors, for 15+ years, far exceeded anything intel, but that time has passed, and they know it. apple is currently transitioning it's cpu's from moto to the PPC 970's that IBM uses in its high end servers.
there are rumors that apple is even switching to intel. this is probably not a bad idea.
the OS is what apple can do that no one else has been able to pull off, and they have done it better than anyone in the industry since 1977, regardless of marketshare. userbase has never equated pure ability or power on an OS level. this is demonstated by rivalries such as beta vs. vhs, linux vs. unix, barney vs. teletubbies, etc.....
and the extra expense you speak of, it will always be there. one will always pay more for a premium product. the userbase for ford mustangs will always be greater, but porsche 911 GT3's will, strangley, always be more expensive.
omg, here i go again.likening macs to high end feel good sport luxo cars. i'm going to hell aren't i =\