To be honest, I've done the whole - let's buy a bunch of food and drinks and then all dip in thing - and I hated it. I like to have my own meal of however much I want to personally have, so I'd rather just pay for myself. Yes, it's a bit selfish, but basically I'm not paying for you nerds. If I am feeling particularly nice I may chip in for a bottle of chamapagne or something that can be shared all around.

EDIT: If we do the catering/buffet type thing like Shorty suggested, I can chip in, but I hate that idea too unless you get duplicates of everything. I will not be happy if there isn't enough of something I want to stuff in my mouth. I will be hangry. No one wants to see me hangry.