First, have you not come up with a price structure already? If not then that is the first thing you need to do. You have to add up all the cost involved in making the cake and then figure out how long it will take and decide what you want to be paid hourly. This would be the bases for your price but you also have to do some research in your area to see what other bakeries are charging so that you aren't undercutting them. You also have to make sure you are legal in order to sell cakes. To price this particular cake you need to know how many people they need to serve because this may be way too big for what they need. It looks like a 6",8",10",12",14" and 16" which would feed about 240 people.