Need some details: are you doing the whole thing? Meat, sides, drinks, dessert, paper/plastic?
Is so, $20 per is not at all unreasonable. If you cook on-site add another $150 or so. If you need to "hire" servers add $20 per staff per hour.
Southern Brethren BBQ Competition Team
"It's all about getting paid!" - Myron Mixon
"I love being hated in my hometown!" - David Hair
KingFisher Gator Rotisserie cooker, WSM, Stainless 5 burner with IR gas grill, Turkey Fryer, Weber JD Commemorative grill, slightly used Bandera chamber for future use as a cold smoker, Masterbuilt 40" insulated ELECTRIC smoker