Catering Service Fee

My fiancé and I are hiring an outside food caterer for our venue. According to the draft proposal (contract has not been signed), there is a 18% service fee in addition to being billed for the chefs ($1,470 - 7 chefs), servers ($1,050 - 5 servers), and event managers ($700 - 2 managers). I assumed the service fee would cover the cost of the "servicing" portion, but the additional costs are adding up quickly for labor and rentals. There's also a $800 fee for an outdoor kitchen set up (venue location does have an indoor kitchen, but it's their preference to use both). Since the food caterer is hired through a "preferred caterer" of the venue, we are looking at $93/person just for the catering and bartending service, not including table linens, napkins, food or alcohol. Cost is broken down to $64/person for the preferred caterer (will handle most set up and servicing) and $ 29/person for the food caterer (chefs, additional servicing, and rentals). Continued in comments.