Clubs buy trophies based on the number of pre-entries; this is why, in part, there is a penalty for late registration.
Looking at the results from the past year, it'd be difficult to recommend ordering trophies for 3 places in each class... This hasn't always been the case. When I last rode the Support line, which was only a handful of years ago, my age class usually had about a dozen riders. A top three finish was significant and deserved a trophy. However, in 2013 I do not believe that any Support class has averaged more than a handful of riders and most have had difficulty filling the podium. This is a troubling trend and it does not bode well for a financially viable series.