About a year ago, I made a setting of the Litany of Tarski for four-part a cappella (i.e. unaccompanied) chorus.
More recently, in the process of experimenting with MuseScore for potential use in explaining musical matters on the internet (it makes online sharing of playback-able scores very easy), the thought occurred to me that perhaps the Tarski piece might be of interest to some LW readers (if no one else!), so I went ahead and re-typeset it in MuseScore for your delectation.
Here it is (properly notated :-)).
Here it is (alternate version designed to avoid freaking out those who aren't quite the fanatical enthusiasts of musical notation that I am).
It seems like something like airgigs.com seems to be the answer. It has musicians available down into the 50 dollars range.
In so far as the figures there are representative, that suggests that $200 would be the right ballpark for getting a choral work performed. That sounds more plausible to me than a couple of bucks, though I wouldn't be surprised if you could get the price down somewhat from there.