it's still a cheap scene regardless of the number in, that shouldn't be the issue here, you never know how many you will get throught the door wehn promoting. Nighters were a tenner years ago and prices haven't really changed that much yet still comploiants are made?
A decent sound system can cost a few hundred, top dj's command a price of at least £150 so with 4 top dj at an all-nighter, the outlay for not DJ's a step down the ladder, the system and of course venue hire which is usually a few hundred for a large venue, flyers adverts etc, bet not much change out of £2000.