Since it is a failry simple design I would charge my base rate of $3/serving (I charge the same for fondant and buttercream). According to the wilton charts a 8", 12", and 16" will serve 180 so my total cost would be $540 plus a delivery/setup fee. HTH!
I have 24+56+100 = 180 servings. My basic buttercream price for weddings is $4 per serving (and I wouldn't charge more than that as it is plainly iced), so I would charge $720.
$4/serving.. That's my bc price.
In my area I charge 2.50 per serving for buttercream and 3.50 per serving for fondant