Do you really have to have a cake?
Cakes can be in a range any where from $100 to $10,000 or even more depending on how many guests you have and just how extravagant it looks with all the little details. A great way to save money and avoid spending more on the food than your dress? Cupcakes! You may also try doughnuts. Either way it's easier to do and cheaper in many ways. One main way is you do not have to buy those sterling silver cutting knifes and cake tiers. It also saves time witch is actually important. Some guests may get annoyed by having to wait and don't forget the little kids that want to put there fingers in the cake or even the "over grown child" of your family. The cupcakes/doughnuts can be in different flavors also.
(Small tip on what ever you choose: Make sure you know if any of your guests have food allergies.)