A loss leader is a product that is sold at a loss in order to profit in another way. You could create a product of your own and sell it at a very inexpensive price in order to upsell them to another product.
For example, let’s say you wanted to promote a product as an affiliate. The product costs $197, and you would get approximately $100 in commission for every sale.
You could create a similar product that was not as in-depth as the product you want to promote as an affiliate and sell it for a very inexpensive price. Then promote the most expensive product as a kind of “upgrade” inside your product.
You could also use these inexpensive products to promote physical products. For example, you could write an information product about how to knit a sweater, and include affiliate links for knitting needles, yarn, and other knitting supplies.
Loss leaders are especially helpful for getting people used to buying from you when you’re just getting started. Make sure your loss leaders are quality, so they will trust you in the future.