Pine, Saldana, Pegg, Urban... never done conventions. Anything you buy is going to be coming from someone whose business is such, and in those cases it's all about vetting them.
I can't speak for Pine, Saldana, or Pegg, but Urban has done a number of conventions. He did Xena/Hercules conventions back in the day, and has done Lord of the Rings conventions as well. It's possible he hasn't done cons since joining Trek, but he has indeed done conventions.