You're charging people to come to your party? Thats not a party, its an event and you could get in big trouble for haveng an event without a permit. Besides, if someone invited me to a party then said i had to pay i wouldnt go no matter how good the food was.
Nobody said it was a party for family or friends! Sounds like a catering job to me! Charge at least 3 times your food cost, even 4 times is good! You gotta figure supplies, time, labor etc... You could call a local caterer and ask what they would charge, then charge less than that!