There's cost based pricing and there's price based costing.
Food and clothing, anything with complex supply chains tend to be cost based pricing. As a rule of thumb, it's x3, maybe x4 for a well-branded item like Nike or Calvin Klein. Most innovations are on supply chain. E-commerce was such a big thing because it could cut out one middle man and lead to 30% price cuts or profit margins, and yet all these online shops ended up appearing in malls anyway.
Software is price based costing because there's no fancy supply chain. iPhones may be somewhere in the middle, hardware tends to have the worst of both worlds - high fixed costs and lots of middle men.
A McDonald's may have franchises and may own some restaurants internally, but they don't want to lose money, so they may base it on the lower profit margins - it makes no sense for a burger in one spot to be $4 and a burger in the franchise to be $5; both need to be $5.
Generally luxury brand do use more expensive parts, whether or not those parts add to the quality. And they do have higher profit margins. But the retailers, distributors, etc still take a 30% cut or so. And in the end, Louis Vuitton is still probably making lower margins than Plants vs Zombies.