From the caveat emptor department...Slashdot points out an HDMI cable at Best Buy priced at $1095.99. A typo? Automatic pricing gone wild? No, Best Buy carries a whole line of insanely priced "AudioQuest" brand cables. (Another good reason to not send Best Buy your business.)
Paying a grand for a cable that's not functionally different from a $5 one is most egregious for digital signals like HDMI -- or USB, for which Best Buy will happily take $1,450.00 of your hard-earned money. That's because these are pretty much pass/fail applications: either the bits all make it to the other end of the cable or not, and signal quality makes no difference beyond that line.
But even in analog applications, suckers will buy overpriced speaker cables that work no better than ones ginned up from wire hangers.
Absolute bargain-basement cables might be more likely to fail -- I do have a few el cheapo, came-with-the-product USB and ethernet cables that failed after a short time of use, or even right out of the box. But don't believe for a moment that high-priced cables are worth it.
But at least cables actually have a function in an audio, video, or computer setup. Bold charlatans will sell you all sorts of magic beans to improve your system. My new favorite is the Quantum Temple Bell from Machina Dynamica, which combines audiophile gullibility with New Age-y quantum woo worthy of Deepak Chopra. It "operates quantum mechanically to improve the performance of all audio and video systems....Only $129."
I have a bell just like that that someone gave me as a gift years ago, and if they paid much more than $25 for it I'll eat my hat. Maybe I should go wave it around my speakers and see if it makes them sound better. It just might work -- but not for any reason involving quantum physics.