My club is helping to sponsor an out of town event where at the place of the event, local enthusiasts will be manning the sag. We want to fairly compensate them for their efforts plus some. This is a multiday event (3 days) with 2 of the days taking including climbing of mountains in overall routes. The sag will be stocked with food, drinks and supplements for the participants along with the standard emergency first aid and road repair equipment. The locals that are manning the sag are quite humble and would normally not take contributions since our participants give their bike shop a great deal of business while we're there. We feel a strong need to show our gratitude for their energy and time spent.

Is there an established formula or system for determining the expense of operating such a sag vehicle in an event such as this?