Sorry but this is ballocks! As a promotor you need to cover your costs, and that includes paying the DJ people who have agreed to grace your venue. It's no good saying you don't know how many are going to turn up, you need to treat it as if enough people will turn up and have enough dosh in your old wallet to cover those costs. If punters don't turn up and you lose money, then sorry but don't promote gigs. It's simple really and a promotor should always pay their DJs - end of.......