The cost of affiliate marketing varies depending on the affiliate program. Some programs are free to join, while others charge a monthly or annual fee. The commission structure also varies, with some programs paying a flat rate per sale and others paying a percentage of the sale amount. As a general rule, affiliate marketing is a cost-effective way to acquire new customers and grow your business. However, it's important to choose the right affiliate program and to manage your affiliates carefully to avoid overspending.