That was true a decade and more ago, but hasn't been true for a long time. Match a Mac with a Dell spec-for-spec and the Mac is the same price or a bit cheaper, but the reputation still lingers.
e.g. I want a desktop Mac without an integrated LCD (i.e. not an iMac), and without putting up with laptop class components which compromise performance (i.e. not a Mac mini or laptop).
So my choice is a Mac Pro: starting at $2799(!)
Fair enough, it's an awesome machine (8 cores, great case design, etc), but it's still nearly 3 thousand dollars.
(Aside: I own PCs and Macs, I just feel there's a bit of a gap in Apple's product range there. It's quite possible Apple are right though, and that most people will want to buy a laptop or iMac).