The Apple Tax isn't as high as people think it is. Yes, you can build your own for cheaper, usually. But their prices are comparable or cheaper than other big-name brands for similar hardware. (I'll let you Google the links to prove it: There are always a slew of people checking everytime Apple releases a new machine.)
What Apple does avoid doing is selling the 'just enough' hardware: The low end, barely able to run current software. They design their machines so that the base config will work fine for the average user for several years, without upgrades. This means the super-cheap machines don't exist - you'd need to add RAM or a larger HDD in a year or two, or your graphics processor would barely be able to keep up, and Apple doesn't want people having that experience with their machines.
Now, the current discussion on whether PC's are 'good enough' is a separate point - I'd argue they are, and even several-year old Macs would be good enough. Apple did have an advantage in the statistics this article was looking at: Their latest OS release obsoleted any Mac with 32-bit anything. (Including BIOS.) Which means that part of their sales is probably people wanting to upgrade who couldn't. (Still, it supports any Mac made in the past 4 years.)