Originally Posted by Siigari
In addition, the HDMI cable thing is like this: a higher quality HDMI cable will improve the strength of the audio signal over a long distance. THAT IS ALL. It will not make your video or audio better. It will simply retain more of the data over a longer distance.
Like EvanPitts has said, signal strength can only be improved with an amplifier. But I understand that you are trying make a comparison to lesser quality cables.
Either way, HDMI transmits digital data which is backed up with some error correcting code. Bit errors can be introduced over longer distances from line impedance and EMI. Better shielding and higher purity copper can make a slight difference with cables over 20ft. At that distance I suggest looking at alternative methods for data transmission or changing your setup. Most of the time those expensive cables derive their cost from marketing using the same amount of shielding and copper purity as the cheapos.
OT: I don't go to BB very much unless I need to see a product in person or get it today. Their staff is almost no help so I end up looking up all the answers on my phone. Though BB isn't the only place where I have encountered ignorant employees. I remember going to Lowes for some torx wrenches and all I got was a tool section employee scratching his head. I can't really say for sure that BB has the greatest number of ignorant employees since I've only been to a couple locations and I usually ignore the employees anyways.