A large guest list means more of everything: food, rentals, waitstaff, etc.
Quality and quantity are the main factors when it comes to cost. A greater number of courses often increases price.
From buffet to plated. Different types of services require different amounts of food and a different number of servers.
Are you having appetizers over the cocktail hour? A food truck? Late night snacks? These will increase the bottom line.
Whether having an open bar, limited bar, or no bar at all factors into the bottom line. Serving just beer and wine or offering a single signature mixed drink will keep costs lower.
If outside the designated radius of travel, expect a fee increase.