I'm glad that selling invite is not existing here anymore it keeps the community clean, with so many people getting validated there are more invites to give for beginners, I still believe that IDENA has a good potential in the industry a year from now it will cover a lot,many developers will come in to contribute to this project.
Looking back, I think only one community member (bitcointalk user) was selling invites, railai if my memory serves.
Regarding the Idena potential, well it feels like XRB back in 2017, not many people were involved, and the ones who were got rich.
Selling invite code is actually not very good, considering that this project requires a large community to realize and make it successful. Of course most people will not want to reach into their wallet just to buy the invite code. There are still many ways to get the invite code including following the idena flip school (telegram group).