When you have a large feed, there is usually a very long tail of products that send traffic to your site. Sometimes you can get one or two clicks on a thousand different products. You may not notice the cost of each click on it’s own, but it starts to add up. With a standard Kill Report it’s hard to get rid of the long tail because you don’t have enough metrics.
When & Where
In extreme cases where you cannot stomach the excessive costs of a specific shopping engine (CSE) and you are unable to lower the spend through other methods, it is recommended to send a feed with only the brands that have performed well historically. Keep in mind that by running an inclusion only feed, you are also getting rid of products that may perform well. So keep testing the feed by adding new products and monitor it for changes.
You might stop a lot of quality traffic by sending an inclusion only feed. You might also save your business a ton of money. Keep your eyes open and watch the performance.