"We will report back on this in the next stage of work. But in general, there are some drivers of price sensitivity that we would be more concerned seeing form the basis of a differential pricing practice."
The FCA said it recognised some consumers may "value convenience more than others" and, depending on the context, it might be less concerned about pricing practices that are based on a willingness to pay.
But the regulator said if the reason some consumers are willing to pay more than others is because they do not understand the product, then firms "should not exploit this by charging them a higher price".
The FCA added: "Similarly, there are some firm behaviours that we would be more concerned about.
"For example, if firms actively sought to identify customers who do not understand the product in order to charge them more, we would be particularly concerned."