It was an online opinion, so we don't know for sure if it's the same one they looked at. I'm not comfortable with the Prince autograph. I don't know the other names.
They have a great reputation. I don't know anything about the symbol signature either, though.
I really don't see them going down in Price any time soon, it's really amazing how much there selling for, as much as Lennon, Hendrix etc.
This is a fake signature! Prince never signed anything in 1999.