I've owned a catering company for 8 years. It cracks me up when brides call me and ask "how much is a reception at your facility?"
Like Ed said above, there are a dozen questions to ask. It kills me when people think an event is simply the cost of the food. Also, when you give a caterer a low-ball budget number, you'll be sacrificing something. The caterer won't just give you his $50 menu for $20. You have to discuss the level of food, service, and details.
The cost of food aside, you realize wine prices can fluctuate wildly? If you choose a low budget price, you'll get cheaper wine and food. It's that simple.
Discuss with a professional caterer the type and level of service you want, then eliminate or reduce items based on your budget.
For a grand ball-park number, I'd charge at least $100 per person for 5 courses, all with wine, in a private venue.