People have their reasons (traffic, etc.) and it may not be their fault, per say.
As a host myself, I know how annoying it can be to have people come after a certain time when the event was meant to begin.
That being said, rather thanhaving an extra fee, I always be sure to emphasize the importance of arriving on time in my threads because if anyone does show after the first battle, they aren't going to play in the event. It's as simple as that, since the tournament has started. I feel like it's reasonable since while they can't play in that event they can certainly stay for free play and to hang out. I feel like it's pretty fair, but personally I wouldn't rather have them pay more to get in. The host would still have to redo brackets and potentially add more data to the spreadsheet- depending how late in the event it was, it could really be a hassle.
Having people pay more money is just a negative for them and would probably make them reconsider WBO events in the future. For most of my usuals who are teens, money is pretty tight for them, so if I had them pay extra they probably wouldn't come back, haha.
Also, true lion gale force wall and fee-hee-heenay call