There's definitely an Apple image tax, but it's not such a simple dichotomy as both sides are making it out to be. Apple isn't the best at any price, nor is the MS-ran commodity PC necessarily the best value.
With something like a Macbook, you do overpay for the specs, even taking into account the quality, coolness of the design, and the OS. It's just that commodity builders like Dell, Lenovo, and HP aren't putting anything comparable in play. It's moreso that you have to overpay a little if you want a solid aluminum case than it is an Apple tax -- it's just that Apple is the only company bringing that style to market. It's unfair to fingerpoint and say "you're overcharging" when they're the only game in town unless you want a parts bin laptop.
The reason why Apple charges what it can and maintains the margins that it does is that no one competes directly with them, and its not because of OS licensing. The average idiot doesn't care about OSX vs Vista, they're shopping on aesthetics and a high quality build, Apple gives them that. I don't think anyone in their right mind can argue that the OS is that big of a differentiator, but you'd have to be a moron to say that there isn't any difference in the physical build, even if the specs match on paper.
That's why I finally bought a Macbook. I wanted a metal laptop somewhere in the consumer electronics price range, and the older style MBPs still felt a little too flimsy for me. Although I will admit to one side effect that I didn't anticipate -- OSX is way better on battery life. As a result, I rarely boot Vista, even though I am just as productive on it.
If MS wants to make this an "overpaying for cool" issue, it's implicitly wanting to sell more of its OS. We all know MS doesn't care what the laptop looks like or costs, as long as it runs windows. Maybe they ought to contract out a design that isn't cheap plastic parts, and they might shift more units.