I don't think I agree. Luxury goods are typically defined as both income and price elastic in economics textbooks. I agree that brands can and do employ various marketing strategies like exclusivity, as you describe. This is also true of low elasticity goods like Liquid Death selling expensive water. Still, in a competitive market where the wealthy can choose other designer brands with similar class projection and quality, theory tells us that customers can and do switch, and the market finds a price equilibrium close to the pre-tariff price.