There is a lot going on under the hood (literally!) that sets these cars apart.
Which isn't to say that everyone needs a Mercedes, but there's certainly nothing intrinsically smarter about a Kia over a Mercedes.
Having actually seen the religiously-collected failure data that all manufacturers keep, I can safely say that your impression is incorrect. The budget brands suffer from substantially more expensive failures than the luxury brands, whose failures tend to be concentrated in non-critical systems (power windows vs. your transmission).
The AK-47 analogy doesn't really work here. There haven't been any "mechanically simple" cars since, what, the 80s? The main differentiator here isn't design or technological complexity, it's part selection and manufacturing rigour. So really you're talking about a hand-made M16 done up in a garage vs. a precision-manufactured M16. We're well past the age of "AK-47" cars.
I used to inspect auto parts for a factory that made ball-joints for a couple dozen different auto companies. It was a parts supplier for everything from low end asian cars to Humvees, Corvettes, and BMWs.
The part selection you speak of isn't always better. When we pulled defective parts off the production line, they were inventoried and put into storage in case the factory failed to meet their quota. When this happened, the defective parts were shipped to the auto manufacturers along with the good parts.
That being said, I agree that there's nothing wrong with owning a luxury vehicle. People have to take a look at their own finances and determine what the best decision to make is. For the average American, it is much smarter to buy a KIA, because the average American can't afford a Mercedes/BMW/etc. If a person can afford it, then good for them.
My stepfather had one with such a problem, and stopped buying BMWs after being a loyal customer for 30 years - his BMW 2002 (model, not year http://en.wikipedia.org/wiki/BMW_New_Class) he could service for himself, while the newer models he can't even touch.
Edit: example complaint http://www.complaintsboard.com/complaints/bmw-c127.html
Then when they finally do break down, there's like a million moving parts, and the one you have to replace is on back order for five years...
But my car isn't just a tool for me. It's a source of enjoyment. I love driving. And I love driving my car. Really, I love it. I would buy an Audi A4 in a second if I could afford it. If you're only judging based on one axis (reliability), you miss a lot of what goes into the purchase a vehicle. Just because it's your most important criteria, it's not mine.
Someone else can sell Kia's.
Edit: Not sure how that will work out in the tablet market, but it certainly works with cars and laptops.