There is no cost to create an Amazon Storefront. However, as an Amazon seller, you will be responsible for paying Amazon's fees for selling your products, which typically include referral fees and optional subscription fees for additional services, such as access to Amazon's fulfillment network or advertising tools. The exact amount you will pay will depend on the type and price of your products, as well as any additional services you use.
It's important to carefully review Amazon's fees and understand how they will impact your business before you start selling on the platform. You can find more information about Amazon's fees on their website.