The following is a detailed explanation of the process and cost of opening a store on Amazon in 2021:

1. Register an Amazon seller account: First, you need to register an Amazon seller account. Visit the official website of Amazon Seller Center and fill in the necessary information, including store name, contact information, bank account, etc. After the registration is completed, you will become a cooperative seller of Amazon.

2. Category review: After successful registration, you need to choose the categories in which you want to sell products. Each category has specific requirements and review processes. You need to submit the necessary documents and information as needed and wait for Amazon to review and approve it. After the review is passed, you can sell products in that category.

3. Prepare products: While waiting for the review results, you need to prepare the products to be sold. Make sure your products are competitive, including product quality, price, and pictures. At the same time, you need to conduct market research, understand your competitors and target audiences, and develop reasonable pricing and sales strategies for your products.

4. Listing products: After the review is passed, you need to list your products on the Amazon platform. You need to provide detailed descriptions of the products, images, prices, inventory status, and shipping methods. Make sure your product information is accurate and complete, and provide sufficient information for potential buyers.

5. Fulfilling orders: When a customer purchases your product, you need to process the order and fulfill the shipment in a timely manner. Amazon provides a range of logistics and delivery services, and you can choose to fulfill the order yourself or use Amazon's delivery services.

As for fees, Amazon's fee structure is relatively complex, depending on the sales plan you choose, product category, sales area and other factors. Generally speaking, Amazon includes the following fees:

1. Monthly subscription fee: Amazon offers two sales plans, namely the Professional Seller Plan and the Individual Seller Plan. The Professional Seller Plan requires a monthly subscription fee, while the Individual Seller Plan does not.

2. Product sales fees: Amazon charges a certain percentage of sales fees, which depends on the category and price of the product you sell. The sales fee is generally within a certain percentage of the product's selling price.

3. Storage fees: If you choose to use Amazon's warehousing service, you will need to pay storage fees, which will vary based on factors such as the number and size of the goods you store.

4. Logistics and delivery fees: If you choose to use Amazon's delivery service, you will need to pay the corresponding logistics and delivery fees, which will vary based on factors such as the size, weight, and destination of the goods.

Please note that the above fees are only general fee descriptions, and specific fees may change and be adjusted. It is recommended that you read Amazon's fee policy carefully before registering, and consult Amazon's customer service team to obtain accurate fee information. I hope my answer is helpful to you. Please feel free to try opening a store on Amazon, and I wish you success!