I'm not seeing this example as unrelated.

E.g. If a seller knows I've been searching for flu remedies, I've made a social media post related to the illness. Then I go to the pharmacy and everything related to alleviating those symptoms is more expensive for me.

Put simply, if they know you absolutely need something, they will leverage that information.

A larger more powerful organization has leverage over someone by collecting their data, and uses that to extract value from them.