For opens, skaters' fees will make up most of it, but it's a horribly expensive business and a high risk of the organising club losing money on it, which I'd think is a big factor in why there are so few.
While the judges and officials are unpaid volunteers, you do have to pay their expenses and because there are too few of them really, you might have to pay a lot in travel and hotels to get a full panel together.
Even for club competitions, with fewer judges and only a few hours of ice time to pay for, the London adult club has only been able to break even-ish where we've had donations/sponsors (including of trophies, so that we were able to save on prize costs).
