There have been many forums that have had this discussion. If you want all kinds of tech talk then look around, they are not hard to find. From all the reading in these forums about "wire and cables" with all sorts of experts chiming in, you will find this... Speaker wires will make you money, thats all. YOU need to do some home work. If you are in a retail enviroment, set it up. Get a system plugged in with basic 16ga speaker wire, to a nice pair of speakers. Then get a set of higher end "name brand" speaker cables the same length. Try going from the 15- 20cent a foot stuff to 3 or 4.00 ft, do you hear a difference??? You shouldn't.
Now don't forget there are some funky cables out there with "boxes" on one end, these may very well make a difference in the sound, that doesn't mean they have corrected anything, they have just changed things. If someone thinks it's better, great thats their opinion and what they like to hear. Sell them.

Same thing with the Monster audio cables, try them, 40.00 cables vs. 150.00, do you really hear anything to justify the price difference? Go get a nice piece of Canare wire and a couple of rca ends, solder them on, you just made a cable for about 20.00, that will perform as good .
Now video you can see, and there are differences in what you are delivering through a cable, so yes here is where the difference can be dramatic. It doesn't have to be Monster cable, any good video cable can produce a result that can be seen, but you still can't make a bad picture look good.

Have fun with them, find cables you like and trust, you should sell cables with every system, but don't get caught up in all the hype. Do your own research so that you know you are getting the right cable for your clients system.