The cable rack beside the register is one of the most profitable spaces in an electronics store. The reason has more to do with when the purchase happens than with what the cable contains.
Accessories are urgency purchases
A shopper buying a cable usually needs it to complete something already bought or already broken. The alternative to paying is not using the device at all.
That removes most of the price comparison that governs the main purchase. Nobody researches a charging cable for a week the way they research the phone it charges.
Urgency also compresses the search radius to whatever store is closest. Convenience commands a premium in any category, and accessories are where it is most visible.
The manufacturing cost is low and the price is not
Cables and adapters are simple, high-volume manufactured goods with mature supply chains. Unit costs are low and fall further with scale.
The retail price is set against the value of the connected device rather than against the component cost. A cable enabling an expensive device can be priced far above one that looks identical.
Certification and licensing programs add real cost for compliant products, and those costs are genuine. They also provide a justification for a price gap wider than the added expense.
Shelf economics reward small items
Retail floor space is evaluated by the profit each unit of space produces. Accessories occupy very little space and turn over quickly, so they perform well on that measure.
A television occupies a large footprint at a thin margin, while a peg of cables beside it can contribute a meaningful share of the department's profit. The two are sold together for that reason.
Placement at the register or beside the matching product is deliberate, because the decision happens in seconds. Distance from the main product would break the connection.
Bundling hides the comparison
Accessories attached to a main purchase are rarely priced separately at the point of sale. A bundle presented as a package obscures what each component contributes.
Because the main item was the subject of comparison, the attached items inherit a sense of having been included. That impression is worth more than a discount.
Splitting the bundle mentally and pricing each component alone usually reveals the accessory portion as the expensive half.
What actually differs between cables
Real differences exist in conductor quality, shielding, connector construction and the standards a cable is certified to carry. Those differences matter most at high data rates or high power delivery.
For low-demand uses, the performance gap between a certified budget cable and a premium one is generally not perceptible. The premium buys durability and headroom rather than a different signal.
The useful question is what the cable must carry, since specification requirements are the only part of the price that reliably corresponds to something physical.