This is an opinion and not supported by any facts. Is it higher quality than say a eMachine, a low end Dell, HP, Acer PC? Yes. Is it higher quality than say a Dell Precision WS, HP Z series WS, or a Fujitsu notebooks, or some other high end PC? No, they aren't and there are absolutely ZERO facts to support that claim.
The problem with the perception of quality between PCs and Macs is that before Macs got popular again, there was a war of attrition among PC manufacturers that was started by Dell. Dell started under cutting the competition. Dell found a way to make PCs cheaper. That caused Gateway, HP, and all the others to find a way to build cheaper PCs to compete with Dell. As PCs got cheaper, so did the quality of the low end machines. Go to Dells website. Click on For Home, then Desktop PC. You will see Dell offering an Inspiron 546 starting at $269.
Now tell me, what kind of quality do you actually think you're going to get for $269? Have you ever seen a Mac for $269? Apple charges a premium for their products. That profit margin is far above any PC manufacturer. If you subtract that profit margin, the cost to create that Mac would still far exceed $269. Just as a side note, you would never be able to purchase that PC for $269 and have it actually be usable. You will have to tack on several add ons, which they expect. You can still get it for sub $500. A PC that is sub $500 is garbage.
I choose the cheapest Dell Precision workstation then spec it out to what I purchase for our company. (nothing special, no raid, 4GB, 160GB drive, DVD, no extra software like office) It was right at $1,600. A far cry from the $500 Inspiron and a hell of a lot more quality.
Anyone who claims Mac is a higher quality product than a PC is generalizing. It's like saying BMW is higher quality than "car". (no brand, no model, just a completely generalized statement)