Glad we all agree on this.
Using the car analogy is a little flawed.
What is the basic function of a car? Get from point A to B. Cheap or expensive car can also do the same.
But apart from the basic function, there are important secondary functions of a car:
* Safety - as you pointed out. Relevant here are crash test standards, safety equipment like air bags, ABS, EBD, etc.
* Comfort - noise insulation, suspension, etc.
* Handling, etc.
The secondary functions are real and practical. And people will pay more to get these functions because these functions make a real world difference.
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Let's look now at HDMI cables.
Basic function: to transmit the signal from one device to another. In short lengths cheap or expensive cable will be able to transmit signal.
Next, are there secondary functions of the cable that are real and practical?
* Length rating - this is quite important and real, since many people might want to run long HDMI cables (e.g. to projector). Thankfully this is certifiable but you really need to ask about it. Here is where clearly price or brand doesn't dictate performance. Say I need a ~10m HDMI cable to my projector for Blu Ray. Basic bandwidth needed is 4.95Gbps. Look at the table here again:
http://www.audioholics.com/education/cable...testing-resultsA cheapish cable like the BJC Series 1 passes the test. The more expensive Cobalt Cables fail. All the Monsters pass

The WireWorld Starlight 5 at a shocking US$1399.95 fails (though tested at 12m).
* Build quality - a rather vague term, but yes we don't want connectors to snap or pop off. We want cables that can flex and not break internally. Trouble is, since you're so keen on certifications - is there a certification for build quality?
* Safety - I think mainly the building inspectors in USA are fussy about this - whether cables, especially those which are meant to be buried in the wall or ceiling, are safe. They have CL2, CL3 rating certs. Does this really make any real world difference?
So you say expensive cables are due to build quality. First thing, what is the certificate to prove build quality? You claim Monster cables have superior build quality - how can this be proved? Any cert to show for build quality? I'm genuinely interested in this because if I want to buy a cable with better build quality, how can I tell?
Unfortunately there's no organisations/bodies certified cable build quality.
All I can share is this built diagram for Monster Gamelink HDMI for PS3 cable.