Why? Because you have to sell your product. First a buyer has to believe your product is worth at least what you are asking. Second, the more you add cost, the more the retail climbs, making it harder to sell and harder for the buyer to justify the cost. Third, no matter how much a power cord improved the sound, there are folks out there who won't believe it and aren't willing to spend more bucks for something they don't believe helps. Fourth, it is one thing to buy a quality line cord that is mass produced, UL/CSA approved, and is independently tested safe; it is another to make a better line cord in small quantities that adds another 100 bucks to the retail price. It is impossible to compete with economy of scale in manufacturing - that is a factory making 5000 line cords a day and you in your small factory struggling to make quality audio gear at 10 pieces a day.
As for the car / tire improvement, one manufacturer was sued a few years back for doing just that. They chose a 3 season tire that clearly outperformed the 4 season one but was sued when the owner crashed during wet weather. All cars today are sold with all season tires, just for that reason.
As for the car / tire improvement, one manufacturer was sued a few years back for doing just that. They chose a 3 season tire that clearly outperformed the 4 season one but was sued when the owner crashed during wet weather. All cars today are sold with all season tires, just for that reason.