But then everybody's salary stagnating hasn't made the cost of goods stagnate. There's no such simple and direct link between the two.
Because Apple, Tesla and the international market for fungible goods like gas or grain, doesn't care about the stagnating salary in your country. They'll still want X USD for their products.
Example: supermarkets where I live co-ordinate their prices. There are 5 big chains and they all increased prices in tandem (and margins, so nothing to do with increased costs). They get slapped with a 100 miliion euro fine every year or two, but what do they care? It's a drop compared to the amount they profit from the cartelisation.