I always understood "selling data" to be shorthand for the whole metrics-for-ads transaction, seems obviously that "selling" the data itself would be a one-time sale but being able to offer "updated insights" every time someone runs a new ad campaign is repeat business.
I think it's important to distinguish adtech companies from data brokers like LexisNexis who actually sell your data to 3rd parties. Lots of people read inaccurate statements like "Meta sells your data" and interpret that literally.
