Defined as the difference you would pay for a Macintosh computer minus a windows-based computer for near the same specifications (usually around 300 to 200 dollars). Many people say this is purely for the brand name, but is in fact justified by more reasons than just the brand name and operating system.
NON-TECH PEOPLE MAY STOP HERE
The Mac Tax is justified by the extra amount of useful programs you get on a Mac compared to just an updater, windows media, and movie maker. These Mac apps are full programs, and not trials which sets it's value higher than a windows software library.
The Mac Tax is also justified by the basing of the Unix code, which windows does not fully abide by. This Unix code prevents viruses and programs from activating without your permission, and also allows for cleaner coding packages for the Mac Operating System.
Lastly, this tax is justified by the higher standard of specifications. For example, windows based computers come with 1mb of RAM standard, and 2mb max at most retailors and online stores, whereas Macintosh computers come with 2Mb of RAM standard and 4mb max. Many PC fanboys forget to do this research for themselves.
Mac: Hello I just got my new Macbook for $999
PC: Dude, you paid way to big a Mac Tax. I got my dell for 300 dollars, and it has a gigabyte of ram and 160GB of harddrive space, and came with windows Movie maker. Of course I had to pay extra for Microsoft Word and install it myself, but it was okay.
Mac: Well, My computer has 2mb of RAM and 320GB of hardware space, came with iTunes, iPhoto, iCal, iChat, photobooth, iWork, and a lot of other applications. And I didn't have to install them.
PC: what is iPhoto? And I thought iTunes has to be downloaded.
Mac: Not on a Macintosh. It just comes with everything I need.
The extra money that you pay when buying a Mac as a opposed to a computer with the same specs from another manufacturer. Some people consider the Mac tax to be a good trade-off, others do not.
"My new iMac was 1500 bucks."
"WTF, why'd you pay the Mac tax, you could've gotten a Dell for like half that."
"Um... Because now I have an operating system that works, from a company that doesn't have monkeys for tech support?"