The difference is that the customer doesn't get any data on this case, not even anonymised. Generally "sell" implies that the thing being sold is transferred i

The difference is that the customer doesn't get any data on this case, not even anonymised. Generally "sell" implies that the thing being sold is transferred in some way, but that's not happening here. The data remains with Facebook. It's like going to a restaurant and buying a meal. They didn't sell you the oven, they just used it to make your food.