The average cost of a wedding cake is $543, according to The Bridal Association of America. The more people you need to feed and the more elaborate you want your cake to be, the more it will cost you.
I recently found out about the genius of "fake cakes." Fake cakes are made out of styrofoam and are elaborately decorated with real frosting or fondant, just like any other wedding cake.
A couple can rent a faux cake, use it during their party (for photos, etc) and share the traditional first bite of cake by hiding a slice of real cake in a small compartment at the back. Then your cake will be whisked away to the back to be "cut", but really less expensive sheet cakes will be sliced and served to guests.
None of your guests will notice, but on the off chance that they do, who cares? At least they get to eat cake.