> There are already concerts with paid tickets going on in platforms like Fortnite, that just happen to be able to act as multi-user VR environments, even though that wasn't their designed purpose. The demand is real.

You have that the other way around. Fortnite was able to host a concert because people like to play Fortnite. There is no demand for VR concerts, there is perhaps some demand for concerts in already-populated online spaces.

People aren't flocking to Fortnite because of the concerts. People who play Fortnite are flocking to these concerts when they happen in their game.