The reason why Premium Shopify themes tend to be more costly is because of the increased value they offer in terms of design features and flexibility. These themes typically include a wide range of advanced design elements and customization options that enable store owners to create a unique and visually appealing storefront. Additionally, they often come equipped with pre-built applications that are seamlessly integrated into the code, providing users with a range of useful functions and enhancing the overall user experience. All of these features combined contribute to the premium pricing of these themes, as they provide a superior level of quality and functionality compared to standard themes.