Sell-through campaigns drive immediate sales. They can be a great way to generate revenue quickly. So why not use them exclusively? You might think of it this way: Suppose a grocery store where you seldom or never shop advertises incredible discounts on bread and milk. If you go to the store and buy only the advertised specials, the store's advertising campaign has failed. Yes, the store induced you to come in and purchase, but its real goal was to convert you into a regular customer, or at least convince you to buy some of the higher-margin items. Sell-through campaigns can suffer similar shortcomings: To induce customers to come and buy, you probably have to offer something that immediately identifies your offer as a real bargain. This "loss leader" approach only works if it allows you to sell high-margin items in conjunction with your bargain items.

Sell-through campaigns are measured on a cost per action (CPA) basis. CPA pricing goes one step further than CPC pricing in that the advertiser pays only when a specific action, in this case the completion of a sale, occurs. CPA provides great accountability; however, you can also expect to pay a significant amount for each sale. You measure your ROI on this kind of campaign by dividing the total sales generated by the cost of the campaign.