We recently went to a wedding in which the bride and groom had done something amazingly cute and thrifty with their wedding cake. They made the decoration for the top of the cake themselves using large wooden clothes pins.
So yes, you could spend $50 - $300 on a very expensive decoration for the top of the cake.
Or you could just use some creativity and decorate it yourself.
People at the wedding thought it was so cute they were taking photos of it.