There are cables, and then there are cables. The differences between these cables and those cables aren't always immediately apparent, but one that immediately smacks you upside the head is the price. Pop into Maplin for a 3m USB cable (the kind that gets bundled with a new printer or scanner) and you'll pay £10.99 for it; look on eBay and you can pick up the same thing for 99p – which, improbably, includes postage.

If you're after a 1m HDMI cable to hook up your HD television to a Blu-ray player or satellite box, John Lewis will sell you one (a 1250 HD Monster cable) for £79.95 – but again, eBay yields one up for 99p. Whether you're buying phono cables, power cords, digital audio cables, speaker cables, FireWire or scart leads, you'll find lavishly packaged chunky ones with connectors hewn from slabs of precious metal for megabucks, and modest ones in plastic bags for the fraction of the cost. The problem we face as consumers is two-fold.

What benefit might we gain from splashing out for the pricier cable, and what might we be missing out on for being a cheapskate? This debate has raged for years; purchasers of expensive cables are dismissed as gullible idiots, vendors accused of selling snake oil, while both retaliate fiercely with statistics to support their cause.

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"Some companies certainly deserve to be chastised or challenged for things they've said," says Bob Abraham, founder of QED, a leading British audio/video cable brand. "Our industry hasn't done itself any favours by making claims that can't be substantiated." But Bob rejects the assertion that all cables are "the same".

"If you connect a short HDMI [High-Definition Multimedia Interface] cable between your Blu-ray and your TV," he says, "it'll work, if it meets the HDMI specification. The assumption is that because it works, it's perfect. There's a belief that because it's digital – just ones and zeroes – the signal is either there, or not at all. But that's not the case. There can be bit errors and timing problems, and these can be improved. People need to be made aware that there are better alternatives. Whether they then choose to buy them or how much they pay is down to them."

The debate surrounding HDMI is particularly fierce, thanks to it becoming the standard interface on modern audiovisual gear and the exorbitant sums that can be charged for cables at point of sale.

Back in 2008, it was described as an "innovation that has changed the world", but that innovation has come at a considerable cost to the unwitting consumer. A spokesman for Which? maintains that HDMI cables under 2m in length will all give the same level of performance, and also casts doubts on the issue of durability. "More expensive cables may prove to be more durable," he responded, "but do you need cables to be durable when they're plugged in and remain plugged in until you decorate, move house or change equipment?"

Jon Jeary, QED's electronics engineer, defends his work. "My job is to design a better HDMI cable, and that cable does have an effect on the signal. It has capacitance, so the voltage changing from a zero to a one has got to charge up that capacitance, which takes time, so the signal begins to round off to a point where you can't tell whether it's a zero or a one anymore."

The pressing question, of course, is whether the bit errors Jeary describes or the timing errors (or "jitter") caused by data failing to arrive at its destination punctually are detectable by the human ear and eye.

Traditionally, this kind of highly subjective issue has caused much argument between hi-fi enthusiasts and those who dismiss their claims as "audio woo". The debate reached something of an apex back in 2007, when magician and sceptic James Randi offered a $1m prize to anyone who could tell the difference in a double-blind test between a $7,000 speaker cable and a much cheaper one.

The challenge petered out in arguments over the finer details of the test, but the prize remains unclaimed and the reputation of high-end cable vendors has undoubtedly taken a hit as a result.

"Out of all the cables we're talking about, it's speaker cables that make the most difference," says Abraham – and most people would agree with him that spending a little more on high-quality wire and better connectors is worth the additional cost.

"But the prices for some of these cables are ridiculous," says Ethan Winer, author of the myth-dispelling book The Audio Expert. He believes that the most compelling reason people are easily fooled into thinking a new audio cable improves the sound is the frailty of human hearing. "As much as we'd like to believe otherwise," he says, "our hearing memory is surprisingly short term. This makes it very difficult to know if subtle differences are real or imagined. Another factor is that the frequency spectrum reaching your ears can change over very small distances in a room."

In other words, the position you're sitting on your sofa could have a more profound effect on the sound than any speaker cable "or power cable!" adds Winer. "Some sell for $20,000. I imagine some salespeople believe this bullshit, but others know full well they are scamming people and yet they do it anyway."

In a sector where claims are difficult to test and gullibility of consumers is relatively high, it's not surprising that jargon features prominently on packaging and publicity material. "Fully annealed 99.99 per cent pure oxygen-free copper" may well mean something to someone, and may well sell the product, but most of us have no idea whether cable is better with oxygen in or without. ("Oxygen-free wire is no better than normal wire", advises Winer.) Ditto "gold-plated connectors", an ubiquitous feature of high-end cabling. "In truth, copper and silver are better conductors than gold," says Jeary. "But gold is used because it doesn't tarnish and oxidise, so in terms of longevity it's better."

Needlessly thick, chunky cabling is often of questionable audiovisual benefit – indeed, some cables are so reluctant to bend that it makes them difficult to plug in. "This is just 'audio jewellery' – pretty to look at and hold, but otherwise has no value," says Winer. "I have no problem with people spending as much as they want on such silliness. I object only when they advise others of what they should buy to achieve good sound."

So, bearing all this in mind, how much should we be spending? Why have market forces not delivered us easily available cables that do the job to the level we require? A few years back, high-street chain Richer Sounds began advising its customers to spend 10 per cent of the price of their system on cabling, but the Which? spokesman is resolute on this issue:

"We don't think you should have to spend 10 per cent of your system price on cables." Bob Abraham, however, believes that Richer Sounds' advice served an important purpose. "It was an attempt to provide a value to these accessories in the eyes of the consumer," he says, "to point out that cables are important. But putting a value on that is really hard.

It was basically saying: 'Allow some money for this'." And there, perhaps, is the only agreement that's likely to emerge from this never-ending debate. How much should we set aside for cables? "Some money."