Self-liquidating offer is a premium offer paid for by the consumer rather than the advertiser. In this way, an advertiser can offer something of value that enhances the product image without incurring any cost.
For example, the XYZ Company sells sugar. On the boxes, a special offer is highlighted for a set of commemorative spoons costing only $3.95. Because the spoons are sold at cost, they may be inexpensive enough to induce the consumer to buy the box of sugar. When, and if, the consumer sends away for the spoons, the cost to the advertiser is fully recovered by the $3.95 payment.
In digital marketing self-liquidating offers are free + shipping&handling offers that are meant to cover the cost of the “free” product and the promotional cost. For example, a free print book and 9.95 s&h on a landing page promoted via Google Search traffic.