There will be over 90 layouts at the show thus weekend. The builders of these railways will have invested a lot of time and money in their layouts and will be giving up Friday and their weekend to be at the show. It is normal normal practice at all Model Railway exhibitions for the organisers to cover the cost of fuel and van hire and also provide accommodation to exhibitors who live too far away to be reasonably expected to drive home and back in the morning. My experience is that, despite these expenses, taking my layout to an exhibition still costs me a little.
Traders pay for space and get no expenses from the organisers. If a show was put on without any layouts then admission could possibly be free.
Unlike many other big shows the Warley NEC show is put on by a model railway club for a model railway club. The exhibition is only a success because Warley club members, members of other local clubs ,layout exhibitors, demonstrators and wives/partners all give their time for free. This is not only the weekend of the show; I spend an average of two hours every week doing work which is purely for the show. I'm happy to do this because I think the event is a great showcase for our wonderful hobby. If those of us involved in organising the show charged for our time admission would have to be an awful lot more.