A retailer turns first-party data into ad revenue by packaging its own shopper records into named audience segments, then selling those segments as targeting on advertising inventory it controls: sponsored product placements and display on its own site and app, plus offsite campaigns on channels like Meta and Google. The retailer is the media owner in this model. Purchase history, loyalty files, and cart behavior become priced ad products, and the margin on that media sits well above the margin on selling groceries or electronics. The whole practice comes down to four moves: build segments from transaction data, attach them to onsite and offsite ad formats, price them at a premium because the data is deterministic and the outcomes are sales-verified, and prove that premium with closed-loop measurement.