I would say with regard to size you would need to ask your customer what size they want it? How many are the feeding etc? Then once you know the size of cake you will need you can work out the cost of all the ingredients and decor and that will lead you to how much to cost once you have figured out your time and other costs. Carved cakes are usually more expensive than round or square as they involve more work. As to how to make it, this is a fairly common style of cake so you will find loads of examples online, you can either carve it or use semi sphere pans.
