fwiw, the most beneficial way of doing this for Costco is also relatively private. That is, companies tell Costco who they want to target and then costco shows

fwiw, the most beneficial way of doing this for Costco is also relatively private. That is, companies tell Costco who they want to target and then costco shows the ads on their behalf. This maximizes value for Costco because advertisers have no alternative to paying Costco each and every time they want to show an ad. It also mostly prevents data exfiltration.