I think it ought to work a little bit like poker; the more players you have, the more prizes there are. So, for example, for 10 entrants there are 3 prizes; for 20 entrants 5 prizes, for 40 entrants 8 prizes. These are only examples but I hope you see where I'm going with it.
Also, I think number of payouts for CC comps should be set by the comp owner.