What's the point of conferences on a CV?
I typically have seen conferences appear in CVs in three ways:


Peer-reviewed conference publications, which in some fields (e.g., computer science) can be as important as journal articles
Talks given at conferences, whether based on peer reviewed papers, non-reviewed abstracts, or invitations, which give evidence that the person has experience with scientific speaking.
Service to the community, whether as an organizer, a reviewer, or a student volunteer.


Beyond that, just saying "I paid $600 to register for this conference and all I got was this lousy tote bag" seems rather pointless.