That's always the rub isn't it. Pun intended
I'm not a caterer, so I don't charge anything more than my costs. I only do this for church and neighborhood events that I'm involved with. But I'd been looking at potentially catering and so I've always tracked my costs for cooks over the years. You'll need to do the same to really know your cost. I know the cost of how much charcoal per cooker, how much wood, how much disposables (foil by the foot, gloves per use, pans, lids) how much consumables (rub by the oz, mustard, juice, etc). All that goes into my cost. I haven't updated my costs this year though with some of the rise in prices and you prices will be different than mine here.
For me though, with tax I'd expect my expenses to be about $165. What you would want to charge is a bit up to you, a flat charge or a per person charge.
The other thing I would think about is, especially if this is your first big event cook, things definitely go wrong. I've gotten into a groove now with big cooks, as others have, but I did that with some low pressure things. I'd be concerned that this is someone's wedding and the first time you'd be doing it. Keeping food hot, how to serve it, making sure no one gets sick. Things to consider.
editted to add:
That would be my expected cost for meat, in pans, served with buns and sauce.
Neil -- "Easy Bake Master"
NB Bandera [gone to heaven...conveniently located in Long Island, NY]
Rebel 23, WSM A, WSM B, UDS, Easy Bake Oven
Pork Pistols BBQ
MOINK...It's what's for linner.