I think that it should cost an extra 20 for the costs I know it's full and all but come on respawn LANs are number 1... that would be mad because I've tried for the past 2 and I either just miss out or don't know it's on ...
If it's only up to 500 registered now, you should be pretty safe to get in even without waiting until they open the doors to anyone. I have to imagine that such a giant spike in early registrations will also mean even more people that don't confirm than normal.