Attendance goal - yes.
"Typical ratio" - no.
In my experience, the public draw has nothing to do with the number of teams or prize money offered. Rather the following determine the turnout, roughly in order of importance:
1) Weather
2) Other features of the event (car show, carnival, kids activities, wet t-shirt contest, etc.)
3) Event Marketing
4) Entertainment act popularity
5) Admission price
6) Date (what competition from other area happenings on that weekend)