Myths. Macs cost all of 10-13% more than equivalent Dells. The bundled software is worth at least that much to many users. The fact you can go to the Genius Bar and get free support long after the warranty is gone is worth a bit, too.
I've been using a 2-button mouse on my Macs for a couple of years -- the support is built in to OSX.
But last year, Apple introduced a five-function mouse.
Edit: not the article I was referring to, but it'll do:
http://kurafire.net/log/archive/2006/04/25/debunking-the-price-myth-apple-vs-dell