If I were to have to pull together a small choir for, say, a wedding or funeral at which was requested "chant and sacred polyphony," I might actually be able to get a group of good musicians together who would say, "we love doing this music so much...we never get a chance to! that we'll do it for free!"
isn't that sad? (the point being: the more "qualified" a musician is, the more likely they are to appreciate and *want* to perform this type of sacred music...but the riff-raff give them barely any chances to!)
however, not to be saying everyone should be taking advantage of this... I think I can quickly ascertain how deep someone's pockets are when they are discussing music for an event. So I would, and I have, said, "yup it'll be $$$ per singer..." but the beauty of what I mentioned at the beginning would more likely happen if someone were like, "we love this music sooo much, but we just can't afford it..." then the musicians might say, "wow, that's just wonderful. of course we'll help you--it's so rare to find someone who appreciates it!"