Q I was in a big-box store shopping for a 55-inch TV, a Blu-ray player and a sound system. Before I even picked out the television, the salesman took me over to a wall with colorful boxes containing HDMI cables and stressed the importance of getting good cables. The cables started at about $99. When I protested, he showed me $40 cables but said I would be compromising system performance with the lower priced ones.

I hadn't realized that cables could be so expensive. Do you think I'm OK with the $40 cables? I'm going to need four cables, one from the receiver to HDTV, and one each to the receiver from the cable box, Blu-ray player and a video-game console.

A At $40 each, you're spending far too much and, contrary to what the salesman told you, expensive cables contribute to a poorer-performing system. (More on that later.)

Given that the holiday season is upon us and that many people will be buying HDTVs, Blu-ray players, sound systems and video-game consoles, it's a good time to warn everyone of one of the biggest scams in consumer electronics: high-priced cables and wires.

The salesman stressed the cables so strongly because the store makes a ton of money when someone falls for this scam, so he is probably under a lot of pressure to sell them.

How bad is this monstrous rip-off? Imagine going into a grocery store for cereal. You see a box of Lucky Charms for $99. When you say it's too expensive, the grocery store employee walks you over to the Cheerios for $40. Paying $40 or $99 for an HDMI cable is pretty much the same as paying $40 or $99 for a box of cereal, because good-quality HDMI cables can be had for about $5.

There's actually a bigger difference in the cereals, because anyone with a functioning sense of taste and smell can tell the difference between them. Despite the pseudoscience and claims made on the cable box, there is no functional difference between a $2,000 HDMI cable and a $5 HDMI cable. HDMI is a digital signal: It either works, or it doesn't.

You can get excellent HDMI cables online for less than $10. I have long recommended Eden Prairie-based My Cable Mart (www.mycablemart.com) and Monoprice (www.monoprice.com), which have nice cables for less than $5. I also like the BlueRigger cables from Amazon, which have solid connectors and strong construction that resembles a nylon rope.

If all cables are the same, why does buying expensive cables mean you end up with a system of inferior performance? It comes down to opportunity cost. Let's say you bought four of the $99 cables, for $396. Now, instead of buying $99 cables, let's say you purchased $7 cables, saving you $368. Take that $368 and buy a better television and better speakers, and you have noticeably better picture and sound quality for the same money.

Send questions to donlindich@gmail.com. Get more recommendations and read past columns at www.soundadviceblog.com.