No, it's not incorrect. It's a phrase that has existed for ages. I don't get your reasoning. He is saying that they don't care at all about the concept of selfies, but they're still potential customers obviously. Saying "could not care less" has nothing to do with whether they are potential customers or not though.
Read this: http://www.englishclub.com/ref/esl/Idioms/C/couldn_t_care_less_427.htm
Read this: http://www.englishclub.com/ref/esl/Idioms/C/couldn_t_care_less_427.htm
