What buying on social media involves — how the deal usually happens, what it is priced by — is the same whatever the subject, so it is written once in the Social guide rather than repeated here.
None of these sellers publishes a rate for an ad spot on social media yet — a gap in what has been read, not evidence that the ad spots are free or unsold.
CVS Health's retail media network using ExtraCare loyalty data for pharmacy and health shopper ads
Ads in PayPal and Venmo plus offsite and shoppable Storefront Ads on PayPal purchase data