In 1973 when I began haunting stereo shops instead of frequenting department stores, the stereo shop salesman I trusted far more than any other I'd dealt with, told me about the ten percent rule. 10% of the system's cost should be spent on cabling.
I don't recall esoteric speaker wire existing back then so I assumed he was talking about patch cords - those things now distinguished by the term interconnects. I myself could not justify spending additional money on something that was included for free with source components like turntables, tuners and tape decks.
When I got into the business myself in 1980, I began to understand the wisdom of his logic. By that time, dedicated speaker wire and upmarket patch cords began appearing with a vengeance, all with huge profit margins. A commissioned sales person would be insane not to at least try convincing a customer to part with more coin to better the weak links in their new audio chain. It was often more profitable commission wise to sell a $70 or $80 patch cord than a $500 component.
As more players emerged in the interconnect / speaker wire scene, I began to re-think quoting the 10% rule on the sales floor. Since the plethora of cord/cable options was on the rise both in choice and price, I upped that number to fifteen or twenty percent. If a customer asked what benefit they'd see by going to a higher model component, I would often counter by suggesting they stay with with what they'd picked and if they were OK with spending more, it should go towards what hooks it all together.
They seemed happy about being enlightened and I was happy ringing in the sale.
