Catering for a friend

I'll be catering a one of my best friends weddings this fall. I will be giving them a HUGE discount. My question is Should I A) Present the invoice showing $$ figures our charges would be for a normal event and then show the discounted price for them below? Or B) Simply give them what the discounted price is without them knowing how much I discounted it?

Honestly I'd like them to know how much I discounted it and go with A) but I'm on the fence as to whether it's the right thing to do. I think they have no clue what it actually costs. What say you?

My reason for wanting to show the normal cost and then the discount is I want them to know what I've done for them. I volunteer every spring for a community event where I cook 400lbs of beef brisket for a fundraiser and I don't get paid a dime (meats are donated by Sysco). The organizers for the first 8 years had no clue the value of what I was donating. Once they found out what the charges would have been if it were not charity (food cost x 2 excludes donated meats) they list me as a major event sponsor and show me a little more respect and not as a cheap hired hand. I'm sure my friend has no clue the cost but what I'm doing for about $13pp would ultimately be closer to $30pp if he were someone else. I won't need a contract for this event, they are very close friends. It would be like asking your mother or sibling to sign a contract LOL Before anyone comments, I'm sure there are a few people who that would be fitting for LOL.