Whoa! The cable can matter a great deal. I was the first to comment that good HDMI cables could be had for between 4 and $10, but I would never dismiss the importance of a good cable.

The big issue is that a lot of cables selling for crazy money aren't necessarily good or even better cables.

But there's definitely the possibility for issues running bad/poor cables on both analog and digital connections.

For instance, try running a 100mbit network on Cat3 cable. Or a gigabit network on cat3 or plain cat5 (not "e").

I'm no electrical engineer, but signal loss, noise and capacity to operate signals at higher frequencies are very real factors that are easy to observe with simple empirical testing.

Even the quality of an optical (fibre) cable is important. A poor cable (including damaged or just badly manufactured) can impede the signal (in this case beam of light).

That said, I have no trouble believing that a cable packed in with a $10 "kit" including all manner of other goodies like cleaners, might very well be bad or poor. However, the cables I listed from Monoprice and Tartan all have really good reviews and are at least the quality of cables costing 10 times the price. Or 100 times depending on where you're looking.