The only thing "premium" about them is their insistence on using milled aluminum for their chassis, but even that comes at a huge price- most of the systems aren't very structurally sound
I'm guessing you've never had the pleasure of repairing an "aluminum"-era MBP? The case design that started back in the PPC era was flimsy as shit. Compared to that, the current models are built like tanks. And I also had a Pismo-era PowerBook, which was flimsier than that.
One major problem was that the optical drive would get out of alignment with the slot in front, and it would be unable to eject discs. Another problem was that the latch wouldn't close because dust or something clogged the little latch thingies. And then there was the surface treatment of the aluminum. There was such a wonderful pattern of pitting where the palms of my hands rested on the case. I had one PPC and two Intel of those, and they were all bad in the same way. I've had a unibody MBP for over two years now (the last of the 17" models, which I promptly downgraded to 10.6, and that isn't easy), and it's just fine, no pitting. And the lid never fails to close. The only place where the case is deformed is over the expresscard slot, which you can tell is a bit sagged if you run your finger along the edge.
I've also fixed my cousin's MBP (I think it's a 2011 15"), which somehow got dropped on the corner with the battery, so a couple of the battery cells popped up. I was able to replace it with a 3rd-party battery and a new hard drive (to replace the aging hard drive that had started to fail, the reason he needed me to fix it). Still built like a tank compared to the older aluminum generation.
But I'll agree with you about the current iMac generation. Not that I would touch an iMac (I always want a separate monitor with a desktop system), but holy crap the display is actually less replaceable than a laptop.