The Dell Insprion cost $359 less than the MacBook, but offered a lot more memory and storage. Ballmer's estimate of a $500 Mac premium may be a tad high, but it's in the ballpark. Let's say the Mac tax is more like $300 than $500.

Apple enthusiasts will counter that Mac users don't have to fuss with security worries, and that's true, at least for now. They'll point out that Macs don't come with the . And they'll make the valid observation that the MacBook's preinstalled software, including iLife, is superior to the so-so apps, including Microsoft Works, that ship with most consumer Windows PCs.

Fair enough. But are those advantages worth a $300-plus premium? In this economy, many consumers may think not.

Ballmer's logo-tax theory doesn't hold true for all Apple products, however. The $199 iPhone 3G doesn't cost more than competing smart phones, even when you add in the monthly AT&T service cost. And iPods come in a wide range of competitively-priced packages, from the $79 to the feature-packed $229 iPod Touch.