I just bought a low-end tower PC from Dell, and they lost money on me. No, not because I scammed them or had some special discount. It's because the new unit had a defective CPU fan from the day it arrived (bad bearings: it wouldn't start or would screech like crazy trying to run). Long story short: they had to send a technician to my house to replace it. (Note: the unit has two fans, one mounted directly on the CPU itself, and one for the box as a whole.)
Since the PC retailed for around $500, there couldn't be much profit margin in it for Dell. Though I haven't checked the various independent research outfits that provide detailed bill of materials (BOM) and costing teardowns, I am sure the cost of on-site call and replacement part (which had to be shipped overnight to the technician) ate into–and likely wiped out–what had to be a very modest margin to begin with. Ironically, a previous Dell unit I bought had a fan that sounded like a jet engine on takeoff; though we never figured out if the fan itself was defective or just being commanded too aggressively, Dell had to replace that fan and its control unit as well.
My very modest tale of woe isn't the point here, however. It's this: today's electronic components are amazingly reliable, and a well-designed and built printed-circuit board (PCB) can also be reliable. (Let's ignore software here.) But every product has mechanical and electromechanical parts, ranging from a “simple” on/off switch to touch-sensitive controls to actuators to fans and latches. These are as important to a successful, reliable product as the ICs, passive components, PCB(s), and other non-moving-part electronics. When a mechanical part fails, the good news is that you can often see the failure; the bad news is that the failure is easily seen and so derided by the consumer as lousy design (“the darn door over the battery compartment broke”)
If you don't give the design and sourcing of these less glamorous parts their rightful place in your design review and sourcing chain, you'll have lots of unhappy customers and lose lots of money. And those are not good things, neither of them. ♦