Yeah the price hike is not proportionate to the upgrade in materials, but the shininess, exclusivity and durability helps to justify it somewhat...
I Think it’s beyond just the price Hike in terms of materials, where it’s likely the amount of research and development, additional health sensors, and let’s be honest, Apple is known to raise prices of their products over the years ‘Because they can’, which has been proven many times with the iPhone, iPad and other products.