"An act--single, duo, trio or entire choir--gets paid on the basis of how they provide what you're selling."

I'm really not sure that you're actually conveying what you mean Dick!!

However, on the basis of your first sentence I'm assuming that you mean that each ACT gets paid pro rata according to the amount of time that they've spent on stage (ie 50% to act 1 and 50% to act 2 irrespective of the number of performers in each group). Have to say that I would have thought that that was the way to do it - not splitting the whole evening's take between the exact number of performers - if act 2 was a choir of 30 members and act 1 was a solo artist, there'd be no justice in splitting it 31 ways.

The punter who's bought a ticket for the evening is presumably paying to see/hear 2 acts - 50% of his/her ticket price is spent on each one.... so it would seem logical to me that the gross take (less 15%) should be split two ways..... personal opinion, of course!