There’s consent from the shopper and the retailer, so it’s not unethical

Two parties can enter an willingly agreement that’s ultimately harmful for both. For the shopper it will limit choice and for the retailer, they’re signing their own death warrant.

Right up until the moment that Comcast does a deal with Facebook to get its agent to not help you get a better rate and perhaps instead lock you into a more expensive contract instead. Remember Facebook’s business model is ads.