They say it is easier to sell to an existing customer than to attract a new customer. Studies have shown that the cost per sale is markedly smaller when selling again to people who are already familiar with you and your products.
Cross-selling and Up-Selling to existing customers is a proven way to increase your profitability as described in this article from the people at Marketing Donut. You already have a relationship with an existing customer. You know which products they have already purchased from you and you can therefore suggest other products that could be useful to them. Sometimes they might want a certain product but didn't know that you supplied it. As they already know you and your brand, they are more likely to stick with you and buy from you again.
You look after your customer and get the sale, and they get the items they want from a supplier they trust. It's one of those win-win situations people crave. ...