My dad is a smart guy so he applied to join Mensa in the 80s. Incidentally he was also an amateur soccer player at the time. Anyway he did the first test which was free and passed it. There was a second test which you did have to pay for but it wasn't that expensive so he did it and passed. But then there was a third test you also had to pay for....so he didn't join. Gave him a good story.

On the rational wiki page for Mensa it says that the founder of the organization left when it was quite young, commenting that conversations between self-validated smart people quickly devolved into "mental masturbation"....

Some of us need the validation because we can't do well in sports. Is every athlete a fool for paying to participate and compete in their sport? Mensa actually had a lot of special interest groups and it filters out people who don't want to have intelligent conversation.