I personally wouldn't consider this a question of moderation, although I have not talked to my comods on this.

One do I've personally organised, because of potential currency fluctuations, we had to add a comfort blanket into conversions between £ and $ - in the event, they stayed within our estimated boundaries, giving us a financial cushion for the event which we used to cover do expenses, provide some extras at the do and donated the rest to charity - we did say at the outset that we would donate to charity any money we had outstanding.

As an organiser, I've seen me spending up at $150 on expenses for ado, not including my own costs of travel and attendance, and that's for a small do with 40-50 attendees. Now, I chose to do that, and chose to put in the time organising as well. However if running a mega do, with 200 attendees, you can't expect the organiser(s) to have to cover all costs of putting on the do. Doing the mega do in London, we quickly realised that even being out by £1 per person on our cost estimates would add up to a large additional charge to be born by the organisers. And of course, that would be in addition to the substantial amount of time going in. But we shouldn't allow Dos to just be the purview of those who can afford to do stuff like that.

My personal feeling is that if a do organiser wishes to get some admin costs back, then I don't see a massive problem with this, so long as the admin fees are reasonable. None of us are professionals at doing this, and if we weren't willing to step up, there would be no dos.