Agree with you there Loggy Driver. I wouldnt suggest it would be easy to set up a show like W&P, I reckon it would take at least 2 years in the planning to get it off. It would take longer to get it known. But " From acorns" etc. It would not be impossible.
As for the exhibitors/stall holders. Im sure they must make there money to make it worthwhile, lets face it, if they werent in it for the cash they wouldnt be there. It would take someone with a lot of land, like Duxford to hold a week log event like that.
It would need a lot of outlay for the initial costs, advertising etc, static costs etc, but it would not be impossible. In fact, thinking about it, it can be done with a group of people, the finaces could be an obstruction.