There is less and less "apple tax" as of today. Go look at Dell's and HP's and probably even Sony's AIOs (we'll get to desktop towers in a moment). Unless you spend about $1,700, you will not even get a dedicated graphics chip. Doesn't matter how powerful Intel's GMA 4500 series are, they will never rival a dedicated ATI or nVidia chip, not even ones that are a few years old. Again, this is for the same price point... not a explanation of a price gap.
Laptops are pretty much the same. Dell's Studio line of notebooks used Intel chips. MacBooks use the nVidia (still integrate I know,) but much more powerful than the latest Intel chips. Same stuff with HP and Sony. Lenovo is no different, most of their computers these days use whimpy Intel graphics vs. the same price point on the MacBook and a better chip.
Towers are were Apple needs a little explaining to do. But still, the same hardware on the Mac Pro is nearly that much money for a PC spec'd alike.
Again, this is only from the graphics chip point of view, I know Dell has a XPS line with dedicated graphics, but the price point... I know HP has lightscribe (who uses it?!?) and Sony has blu-ray (I know other companies have blu-ray but Sony is the most prominent). I haven't mentioned the corner to corner glass bevel of the MacBook vs. some cheapo and last generation plastic housing. Macs are also much more aesthetically pleasing and made of aluminum, which helps vent heat and is much stronger than any plastic out there. The ability to run multiple OS together (Fusion and Parallels) as well as Boot Camp make Macs a much better competition against PCs as of today.
Do a feature comparable match up of any Apple to any Dell/HP/Sony/Lenovo, and the price difference is a total fabrication. (Excluding the Mac Mini) Dell will charge you almost four grand for a Server grade chassis which is scarcely more powerful than the first Mac Pro I bought for $3200.00. . . in 2006.
Last time I checked, Dell makes great looking computers with last generation ideas for hardware type. In other words, crap hardware.
It's a hypopthetical.