Luxury brands spend millions on marketing and brand awareness. In some sense, all the "sales work" have already been done before a person sets foot into a Bugatti dealership. Reputation takes decades to build but just a few missteps to destroy. Brand is way more fragile than people think. As soon as Bugatti stops making great cars, they'll fall into a place where they can't compete in the luxury market, nor the mass market Japanese car brands like Honda or Toyota.
In that sense, luxury fashion seems to be a easier market than watches or cars. You don't need an innovative engineering team. Just spend millions on marketing to uphold the common narrative you are a luxury brand. And that shirts with your logo on it costing 10x more than a similar product at say H&M, is not only justifiable, but sensible.