I guess it depends on where you are... where I live, I could charge about a $1 - $1.50 per serving for it ... other areas you may could charge more.
Ok, I'll try and help best I can. Just logged on. I have a pricing matrix from someone on this site who really deserves so much credit. Unfortunately, I can't remember who sent it to me.
Anywho, this is what they have.....
Cost of 12" round 2 layers
serves 56
cake qty 4, cost $9.37
bc icing qty 4, cost $13.70
board 1 @ $.50
box 1 @ $1.80
total cost $25.37
I know from this site they say multiply your cost by 2 or 3 for your price??
So I hope that helps.
To be sure I give credit where it's due, the pricing guide I have is from sugarbeancakes and it's wonderful! It was from a post a few weeks back and she was nice enough to forward it to a bunch of us. I just found the email she sent me in my saved folder and I wanted to give her the kudos she deserves! 
I'd say about $75 considering your doing a FBCT!
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