Buttercream and fondant are the two most common wedding cake frostings. Fondant usually needs to be poured over a layer of buttercream, so the baker is actually making and applying two layers of frosting when using fondant. Here are some frosting price examples:
Specialty Cakes by Amanda in North Richland Hills, Texas:
$3.50+ per slice for wedding cake with buttercream frosting
$5+ per slice for wedding cake with fondant frosting
Sweet Confections Cakes in Harrisburg, Pennsylvania:
$4+ per slice for wedding cake with buttercream frosting
$6+ per slice for wedding cake with fondant frosting